Account Error: Failed to send username. The mail server pop.xxx.xx responded: invalid command.

Good morning, Thunderbird was preventing me from accessing one of my accounts, and the support team for that account told me that changing the password would resolve the issue, as is the case for all users of that provider. Instead of changing the password, I deleted the POP server credentials line for that account. Since I received the error I mentioned in the header of my question the next time I tried to download messages, I simply changed the password for the SMTP server credentials, which now works. I asked Thunderbird to ask me for the password again to access the POP server, but even though the credentials line reappeared with the correct information, Thunderbird continues to give me the same error, while I can connect to the POP mailbox with other programs or via webmail. How can I resolve this issue? Thanks in advance for your help.