I have been fighting a losing battle with Horcrux and backups. At first it was my iCloud account which couldn't connect even though I had used an App Specific password. I removed the account and tried again. Same thing. I went ahead and tried twice more with 2 more App Specific passwords. No luck.
Now I have gone 2 weeks without a back up to my comcast.net email. At first I thought it was 2FA, but since Xfinity does not use app specific passwords I couldn't understand the connection problem. So, even though I was hesitant to do it I disabled 2FA on the account. That didn't help either. I can sign into the webmail version just fine with my username and password but Horcrux seems unable to do so.
This is beyond frustrating. I just decided NOT to backup my iCloud account and if the Xfinity account fiasco can't get solved in a day or two it's goodbye to Horcrux. Which I've been using since 2018.