TradeSkillMaster (TSM) Login Problem

Hey folks - I need some help, I think…

Installed TradeSkillMaster Desktop App using the installer script provided on lutris.net. In the configuration the starter is set to GE-Proton (Latest). The app is indeed starting and asking for a username/mail-address and password.

If I provide both and hit the login button it takes ages and finally shows a message:
“Unknown error. Please try again later.”

Can’t do anything in the login window after this message showed up.

TSM Desktop App is v4.14.1

Anyone having the same issue, or better… a possible solution?

Cheers and thanks in advance!!!