It might happens you start getting cpanel/whm default page for all the domains.
Follow the steps in order to resolve the issue:
Run following command:
This command helps to restores the missing alias in the userdata and merge it with your existing data.
This command helps to builds the httpd.conf against the merged userdata.
If still you get cpanel/whm default page then check name server ip’s.
Update name server ip’s from whm –>> name server ip.
Thats it. The domains should work fine now.