You need to check the DNS report from intodns and fix if there is any errors in it. If you are not good in troubleshooting the dns issues, please check with your support to track the issue.
Since ns1.midomain.com and ns2.midomain.com are for name servers, there is no need to work the URL in http and https. Make sure the dns entry for these subdomains should work. Use the following command to track the dns resolution for the ns1 entry. Do the same for ns2 as well to identify the issue.
dig A ns1.midomain.com +trace
If all the domains are setup NS as ns1 and ns2 and some domains work and some domains not working, then the chances are the dns records are properly setup for the name servers. If you provide your domain name, I can check the reports and give more inference about it.