Not able to LogIn

Hi, since two weeks I am not able to log in into my perch account. Saying:

Sorry, your license key isn't valid for this domain. Log into your Perch account and add the following as your live or testing domain: cms.upclassics.com

I went to my Account and changed it to cms.upclassics.com - but nothing happened. And why came this up immediately, before we had no problem since we created the account

Our admin who did the installation and has experience with Perch left unfortunately.

Thanks for your help