Connect my roundcube e-mail with Thunderbird don't work

[megapanda]

I'm not able to connect my e-mail with thunderbird. The error report says: Login to the server failed. Maybe your configuration, username or password is wrong.
But I'm 100% sure, that the username and password is correct and I adjusted the configuration many times without success. I was able to connect the e-mail with outlook and the win 10 app, but it showed me first the error that there is problem  with the certificat (error code: 0x80072F0D). I was able to ignore the error and the e-mail was connected but I wanna use thunderbird again.
Please excuse my english, I'm German.

[JohnDoh]

Roundcube is an email client, like thunderbird but web based. For help configuring other clients please contact your email provider.