Please confirm if you can sign into Gmail from a browser using the same password.

Thank you but I have fixed the issue. I ended up having to go into the options and deleting all saved passwords. Once I did this and restarted my computer I was able to set it up and again successfully.

You're welcome. The screenshot you posted twice clearly shows your email address. This is not advisable; you shouldn't post your personal information in public forums like that. I'm not sure if you can edit the posts and remove the screenshots, so try it and in future screenshots, edit/mask such information.

Thanks for the advice - Screenshots deleted now.

Trying to delete them. Might have to delete the entire post.

I'm having exactly the same trouble -- and this is my primary email account. And yes, I can sign into that email account in other browsers. Please help!

I fixed it by going into Thunderbird, Menu, Options, Options, Security, Passwords, Saved Passwords. I then deleted ALL saved passwords, then went back to the start to set up a new account from scratch. This fixed the problem completely for me.

If you're on a MAC, you go to Preferences and then follow the above directions (from Eric). Thanks so much!