Regex not working in Okta


I am trying to define a Regex pattern for my Identity Provider to only allow certain users from a certain domain.
After a bit of trial and error, I found this input that I have been using until now: .*$
However, it seems I need 2 more domains ( and I dont really know regex, but after some research and guessing, I was able to find a string that I got working in
New input: (?i)(?:.*$|$|$)

I added the (?i) to ensure that its case insensitive.
This new Regex doesnt work. My Okta keeps rejecting the user I use for testing.

What am I doing wrong?