Cannot link thunderbird to my email with new computer.

I just bought a new desktop computer. It is a Lenovo using Windows 11. I downloaded Thunderbird (.exe) and attempted to install. The installation program does not recognize my credentials. I get an error message that says "Authentication error. Unable to log in at server. Probably wrong configuration, username or password." I have tried every variation I can think of, but no luck. I enlisted Best Buy Geek Squad, and over 2 hours later they have determined that the computer itself has no problems--it is Thunderbird that is refusing to recognize my credentials. I have 4 other devices--2 Iphones, an Ipad, and a laptop using Windows 10, and all have been, and still are, using Thunderbird with no issues. How do I get Thunderbird to recognize my credentials, which are valid on 4 other devices?