On the toolbar > Options (click on the >) Account settings.

Are there any accounts listed? What about in outgoing server (SMTP)?

Whenever I do this and click on anything on the left hand side in the accounts settings I get the account wizard states "An account with this name already exists. Please enter a different account name."

I have opened the troubleshooting information page. I have included it a screenshot. For the most part it seems to conform to yahoo.com's requirements although in the imap in outgoing services I see the information there duplicated with one default marked as true and one marked false.

The reason I'm looking at this is that Thunderbird says it needs a password. In Yahoo I use an app generated password when needed for Thunderbird. It will not accept the character password Yahoo gave me for Thunderbird. I have been entering them both with the spaces between every 4 characters and without the spaces.

Number lock was off. I meant to write: "It will not accept the 16 character password Yahoo gave me for Thunderbird. I have been entering them both with the spaces between every 4 characters and without the spaces.

paulycc said

Whenever I do this and click on anything on the left hand side in the accounts settings I get the account wizard states "An account with this name already exists. Please enter a different account name."

Is it so hard to change the account name in the pane in front of you? (I think you will find the cursor blinking in the field you need to edit.

Ahh jeez, I was making that a lot harder than it needed to be didn't I? Time for me to retire my alter ego of Captain Obvious. Thank you.

That you have two accounts with the same name would indicate you have added the same account more than once. When you have trouble with an existing account, removing it is probably the least productive thing you can do, Short of ring your ISP and ask them.