Can you log on to your webmail account using a browser. Please check, if you can then you know that the password is good. If webmail asks for you to update the password then do so. Then recheck that the new password gets you access to webmail.

In Thunderbird, remove the stored password.

• Tools > Options > Security > Passwords tab
• click on 'Saved Passwords'
• click on 'Show Passwords'
• select both mailbox and smtp passwords for the account
• click on 'Remove'
• click on 'Close'
• click on OK to save changes to Options.

• Close and reopen Thunderbird.

It will ask for password, enter password at prompt and select the checkbox for password manager to remember the password. click on OK.

I did the above, pass word was still not recognized. I did notice when I went to do this part of the instructions: select both mailbox and smtp passwords for the account there was only one, not 2 passwords to delete. Can you help me further please?

Confirm: Did you have a mailbox password or an smtp password or both for the mail account? which one was missing if any?

I think mailbox. This is what the Saved Passwords box shows :

Site: mailbox://pop.cox.net (mailbox://pop.cox.net) user name: sunbunibrown Password: xxxxxxxx

Are you able to logon to webmail using a browser with that password?