A little detail would be helpful, if you expect a diagnosis. For example:
Do you have a reseller account (with access to DNS Zone), or just a regular shared hosting account?
How did you create the sub-domains?
Did you set up cPanel Redirects?
Did you make any .htaccess entries that affect these domains?
What did you do differently for the sub-domains that are working, versus the ones that are not?
If you don't accurately describe what you did and what issues you encountered, we can't very well help you.
I am not WHB staff and I am not paid.
I provide help in these forums on my own time.