Thunderbird is email client software running on your computer. Thunderbird has nothing to do with administering your email account details. That is done with your email provider. If you are using the password reset form on this support forum to try to reset the password for your email account you are wasting your time. This forum and your email account with your email provider are two different things. Most email providers have a password reset link on their email help page.

The problem seems to be that the password accepted by the provider is not acceptable by Thurderbird. What do I do without changing the provider's password.

If you know you have a working password, it works when you log in at the providers web mail page, then you have incorrect server settings or your antivirus software is getting in the way. Thunderbird could care less what your password is. It presents the one you provided to the email server of your provider that accepts it or rejects it.