Another common issue is server load - if the load is too high the backup system will pause and wait for a less busy time to try and complete.
You should be able to check /usr/local/cpanel/logs/cpbackup or /usr/local/cpanel/logs/cpbackup_transporter to get more details on the issue happening.
this is what happens after creating the Backup File,
the problem is in the transfer
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Initializing log file
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] cpbackup_transporter - parent starting
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] cpbackup_transporter - child starting
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] cPanel Backup Transporter Queue Daemon started.
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] cpbackup_transporter - started
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] cpbackup_transporter - Checking queue for tasks
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] cpbackup_transporter - Processing next task
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Instantiating Object
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Starting a "copy" operation on the "mysite Storage" destination ID
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Validating destination path 2021-07-09/accounts/
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Making Path 2021-07-09/accounts/
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Path creation successful
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Uploading account backup /backup/2021-07-09/accounts/wwwmysiteit.tar.gz to 2021-07-09/accounts/wwwmysiteit.tar.gz (from 2021-07-09/accounts/wwwmysiteit.tar.gz)
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Attempting to upload /backup/2021-07-09/accounts/wwwmysiteit.tar.gz to 2021-07-09/accounts/wwwmysiteit.tar.gz for destination: mysite Storage
[2021-07-09 03:20:09 +0200] info [cpbackup_transporter] Upload attempt #1 starting for /backup/2021-07-09/accounts/wwwmysiteit.tar.gz to 2021-07-09/accounts/wwwmysiteit.tar.gz for destination: mysite Storage
[2021-07-09 05:20:09 +0200] warn [cpbackup_transporter] Upload attempt failed: Time out reached for upload attempt #1
at /usr/local/cpanel/Cpanel/LoggerAdapter.pm line 27.
Cpanel::LoggerAdapter::warn(Cpanel::LoggerAdapter=HASH(0x16b8be8), "Upload attempt failed: Time out reached for upload attempt #1\x{a}") called at /usr/local/cpanel/Cpanel/Backup/Queue.pm line 658
Cpanel::Backup::Queue::transport_backup::attempt_to_upload_file(Cpanel::Backup::Queue::transport_backup=HASH(0x149b6e8), Cpanel::Transport::Files::SFTP=HASH(0x24aaba8), "/backup/2021-07-09/accounts/wwwmysiteit.tar.gz", "2021-07-09/accounts/wwwmysiteit.tar.gz", Cpanel::LoggerAdapter=HASH(0x16b8be8)) called at /usr/local/cpanel/Cpanel/Backup/Queue.pm line 333
Cpanel::Backup::Queue::transport_backup::process_task(Cpanel::Backup::Queue::transport_backup=HASH(0x149b6e8), Cpanel::TaskQueue::Task=HASH(0x24aaa28), Cpanel::LoggerAdapter=HASH(0x16b8be8)) called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 635
eval {...} called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 638
Cpanel::TaskQueue::__ANON__() called at /usr/local/cpanel/Cpanel/StateFile.pm line 241
eval {...} called at /usr/local/cpanel/Cpanel/StateFile.pm line 241
Cpanel::StateFile::Guard::call_unlocked(Cpanel::StateFile::Guard=HASH(0x249b080), CODE(0x2341268)) called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 643
Cpanel::TaskQueue::process_next_task(Cpanel::TaskQueue=HASH(0x249ad08)) called at /usr/local/cpanel/bin/cpbackup_transporter line 168
eval {...} called at /usr/local/cpanel/bin/cpbackup_transporter line 166
[2021-07-09 05:20:09 +0200] info [cpbackup_transporter] Upload attempt #2 starting for /backup/2021-07-09/accounts/wwwmysiteit.tar.gz to 2021-07-09/accounts/wwwmysiteit.tar.gz for destination: mysite Storage
[2021-07-09 07:20:09 +0200] warn [cpbackup_transporter] Upload attempt failed: Time out reached for upload attempt #2
at /usr/local/cpanel/Cpanel/LoggerAdapter.pm line 27.
Cpanel::LoggerAdapter::warn(Cpanel::LoggerAdapter=HASH(0x16b8be8), "Upload attempt failed: Time out reached for upload attempt #2\x{a}") called at /usr/local/cpanel/Cpanel/Backup/Queue.pm line 658
Cpanel::Backup::Queue::transport_backup::attempt_to_upload_file(Cpanel::Backup::Queue::transport_backup=HASH(0x149b6e8), Cpanel::Transport::Files::SFTP=HASH(0x24aaba8), "/backup/2021-07-09/accounts/wwwmysiteit.tar.gz", "2021-07-09/accounts/wwwmysiteit.tar.gz", Cpanel::LoggerAdapter=HASH(0x16b8be8)) called at /usr/local/cpanel/Cpanel/Backup/Queue.pm line 333
Cpanel::Backup::Queue::transport_backup::process_task(Cpanel::Backup::Queue::transport_backup=HASH(0x149b6e8), Cpanel::TaskQueue::Task=HASH(0x24aaa28), Cpanel::LoggerAdapter=HASH(0x16b8be8)) called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 635
eval {...} called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 638
Cpanel::TaskQueue::__ANON__() called at /usr/local/cpanel/Cpanel/StateFile.pm line 241
eval {...} called at /usr/local/cpanel/Cpanel/StateFile.pm line 241
Cpanel::StateFile::Guard::call_unlocked(Cpanel::StateFile::Guard=HASH(0x249b080), CODE(0x2341268)) called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 643
Cpanel::TaskQueue::process_next_task(Cpanel::TaskQueue=HASH(0x249ad08)) called at /usr/local/cpanel/bin/cpbackup_transporter line 168
eval {...} called at /usr/local/cpanel/bin/cpbackup_transporter line 166
[2021-07-09 07:20:09 +0200] info [cpbackup_transporter] Upload attempt #3 starting for /backup/2021-07-09/accounts/wwwmysiteit.tar.gz to 2021-07-09/accounts/wwwmysiteit.tar.gz for destination: mysite Storage
[2021-07-09 09:20:09 +0200] warn [cpbackup_transporter] Upload attempt failed: Time out reached for upload attempt #3
at /usr/local/cpanel/Cpanel/LoggerAdapter.pm line 27.
Cpanel::LoggerAdapter::warn(Cpanel::LoggerAdapter=HASH(0x16b8be8), "Upload attempt failed: Time out reached for upload attempt #3\x{a}") called at /usr/local/cpanel/Cpanel/Backup/Queue.pm line 658
Cpanel::Backup::Queue::transport_backup::attempt_to_upload_file(Cpanel::Backup::Queue::transport_backup=HASH(0x149b6e8), Cpanel::Transport::Files::SFTP=HASH(0x24aaba8), "/backup/2021-07-09/accounts/wwwmysiteit.tar.gz", "2021-07-09/accounts/wwwmysiteit.tar.gz", Cpanel::LoggerAdapter=HASH(0x16b8be8)) called at /usr/local/cpanel/Cpanel/Backup/Queue.pm line 333
Cpanel::Backup::Queue::transport_backup::process_task(Cpanel::Backup::Queue::transport_backup=HASH(0x149b6e8), Cpanel::TaskQueue::Task=HASH(0x24aaa28), Cpanel::LoggerAdapter=HASH(0x16b8be8)) called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 635
eval {...} called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 638
Cpanel::TaskQueue::__ANON__() called at /usr/local/cpanel/Cpanel/StateFile.pm line 241
eval {...} called at /usr/local/cpanel/Cpanel/StateFile.pm line 241
Cpanel::StateFile::Guard::call_unlocked(Cpanel::StateFile::Guard=HASH(0x249b080), CODE(0x2341268)) called at /usr/local/cpanel/Cpanel/TaskQueue.pm line 643
Cpanel::TaskQueue::process_next_task(Cpanel::TaskQueue=HASH(0x249ad08)) called at /usr/local/cpanel/bin/cpbackup_transporter line 168
eval {...} called at /usr/local/cpanel/bin/cpbackup_transporter line 166
[2021-07-09 09:20:14 +0200] info [cpbackup_transporter] cpbackup_transporter - Processing next task
[2021-07-09 09:20:14 +0200] info [cpbackup_transporter] Instantiating Object
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Starting a "copy_backup_metadata" operation on the "mysite Storage" destination ID
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Uploading backup metadata file /backup/2021-07-09/accounts/.master.meta to mysite Storage
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Validating destination path 2021-07-09/accounts/
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Path exists
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Uploading backup metadata /backup/2021-07-09/accounts/.master.meta to 2021-07-09/accounts/.master.meta (from 2021-07-09/accounts/.master.meta)
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Attempting to upload /backup/2021-07-09/accounts/.master.meta to 2021-07-09/accounts/.master.meta for destination: mysite Storage
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Upload attempt #1 starting for /backup/2021-07-09/accounts/.master.meta to 2021-07-09/accounts/.master.meta for destination: mysite Storage
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Successful transfer of /backup/2021-07-09/accounts/.master.meta to 2021-07-09/accounts/.master.meta for destination mysite Storage
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] The backup has been successfully uploaded at least once, now we will delete the local copy (/backup/2021-07-09/accounts/.master.meta) since keeplocal (0) is disabled.
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] cpbackup_transporter - Processing next task
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Instantiating Object
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Starting a "prune" operation on the "mysite Storage" destination ID
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Performing prune operation, retaining 2 items on: mysite Storage
[2021-07-09 09:20:15 +0200] info [cpbackup_transporter] Pruning backup directory: 2021-07-07, from mysite Storage
[2021-07-09 09:20:32 +0200] info [cpbackup_transporter] cpbackup_transporter - Processing next task
[2021-07-09 09:20:32 +0200] info [cpbackup_transporter] Removing backup staging directory: /backup/2021-07-09
[2021-07-09 09:20:43 +0200] info [cpbackup_transporter] cpbackup_transporter - Processing next task
[2021-07-09 09:21:12 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 270s for new tasks
[2021-07-09 09:21:42 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 240s for new tasks
[2021-07-09 09:22:12 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 210s for new tasks
[2021-07-09 09:22:42 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 180s for new tasks
[2021-07-09 09:23:12 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 150s for new tasks
[2021-07-09 09:23:42 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 120s for new tasks
[2021-07-09 09:24:12 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 90s for new tasks
[2021-07-09 09:24:42 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 60s for new tasks
[2021-07-09 09:25:12 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 30s for new tasks
[2021-07-09 09:25:42 +0200] info [cpbackup_transporter] cpbackup_transporter - Waiting up to 0s for new tasks
[2021-07-09 09:25:43 +0200] info [cpbackup_transporter] cpbackup_transporter - Exiting - the queue has been emptied; no more work to do after waiting for 300s
[2021-07-09 09:25:43 +0200] info [cpbackup_transporter] cPanel Backup Transporter Queue Daemon is being stopped.