SubAir Error "400: oops something went wrong"

[sugi]

Hello,

I just wanted to try subAir, but just received a rather unhelpful error message after entering my server name and login data:
400: oops something went wrong.

Server is licensed. Any idea what that could be?

Regards,
Daniel

Update: Forgot to enter the full path where subsonic is reachable. https://my.subsonic.server/subsonic/ instead of only https://my.subsonic.server/