Cannot configure Thunderbird POP3 account on MacOS 27: "Can't find a server"

I've been using Thunderbird for my POP3 accounts on Windows 10 for years. I'm now trying to install Thunderbird on a new Mac Mini (M6) running MacOS 27. In the Thunderbird setup, I go straight to Manual Configuration and select POP3. This takes me to a screen that allows me to configure one POP3 account plus an SMTP server. I enter the exact same configuration info that I use for one of my accounts on the Windows machine. Interestingly there is no box on the form for an account password. When I hit the "Connect" button, Thunderbird post a message saying "Mozilla Thunderbird failed to find the settings for your email account." When I select "Show more" it says "Can't find a server".

My Mac machine has its firewall turned off completely ("Inactive") and I have no problems with other apps accessing the Internet. There is no way to explicitly list Thunderbird as a firewall exception because the firewall is off. Further, I opened a command window and pinged both my POP3 and SMTP servers (using the same names as I supplied in my Thunderbird configuration) and they ping just fine; i.e. "ping" has no problem reaching them. I'm at my wits' end.