Mike,
Your disappointments are understandable.
For us to be accurate on trying to help you in this matter, please provide us the exact error notification/message.
In Windows 10 Fall Creators Update (ver. 1709), the Shared Experiences can be turned off by simply going to Settings > System > Shared experiences > Toggle the Share across devices option OFF.
For initial troubleshooting, you can try the https://social.technet.microsoft.com/wiki/contents/articles/13976.how-to-troubleshoot-microsoft-account-issues.aspx[*Microsoft Account Troubleshooter tool*](http://download.microsoft.com/download/F/2/4/F24D0C03-4181-4E5B-A23B-5C3A6B5974E3/microsoftaccounts.diagcab), and see if it will be able to bring any results in hand. Take of the message-return of the tool and get back to us if there's no single fix applied.
We'll be waiting for your reply. Please remember to bring the exact error notification. That will help us funnel down the issue a lot easier.
Kind regards.