Anyone has issue with error 500 when log into Adobe stock contributor account?

Sorry, I can't help with your error 500 issue.

But for your screenname problem:

Please make sure that every contact does have the Adobe Logo on the bottom right side of his/her avatar and and the lettering Adobe Employee below the name exists.

Here is an example (screenshot) how your contact in the forum should looks like (logo and title):

Please use the following thread for changing your screenname through an Adobe Staff member (eg Silvia_CC )

How to change your community username 

Write your screenname and your wished screenname in that thread.

Hope that helps you a little

Maybe server down will be back normal soon, but I don't know when.... I have same issue with you (from 2 days ago, still stuck with error code : 500 internal server error)....