My ISP suggested I change my password

You do need your password to login to your account on your email provider's server. Hence you'll also have to change your password on the server. You'll have to login to your account via webmail to do this.

Thunderbird can remember your account password so that you don't have to type your password again and again every time it is needed. Presumably you just deleted the password Thunderbird had remembered. But you can't change your account password this way.

Thank you for the reply. I can log onto my email providers server, but I cannot input the new password into my Thunderbird account. I'm not getting a prompt to do so, and cannot do it manually.

I can log onto my email providers server, but I cannot input the new password into my Thunderbird account.

Yes, you need to change your account password on the server.

Just for the record, there is no such thing as a 'Thunderbird account'. Thunderbird is an application running on your device, so it does not provide email addresses, nor the service to transmit emails. But Thunderbird can be used with your existing email address and service provider to send, receive, sort and search your email messages.