Thunderbird does not recognize e-mail provider's settings as valid.

I am trying to configure Thunderbird 91. See attached graphic "Configuration in T-Bird 91 - Password Not Shown.jpg". Every entry on that page is correct. I have verified those entries with my e-mail provider. Yet, the "done button" is greyed - T-Bird for some reason does not like those entries. The second graphic, Configuration in T-Bird 91 - Error Message.jpg" is the error message T-Bird gives me when I try to force it to accept my data. The third graphic, "Sending Myself a Test Message - Error Message.jpg" is the error message I get when I try to send an e-mail to myself. T-Bird is trying to tell me that my use name is my full e-mail address. That is wrong. My user name for this e-mail provider is simply my first name. Suggestions, please.