Go through process to add a Comcast/Xfinity email account. Everything looks right; choosing continue takes me to Xfinity logon page. With proper username ( and third party app allowed in Comcast settings). it then shows the "Let's Go" button. Clicking that results in an ACCESS DENIED/permission issue to the server. Using another browser (including FF) lets me log in fine. Spent 2 hours with Xfinity support who claimed to have made some account adjustments that ultimately did nothing. Would like to be able to add Xfinity account to Thunderbird ( I do have latest version). Thoughts and advice appreciated.