Do you happen to have the ticket number handy? I can take a look into what's going on, however, I can't change the outcome provided by the specialist. ^TK
I would suggest starting off by uninstalling, running as administrator, and making sure your firewall/antivirus has given Minecraft full permissions. ^TK
Sorry to hear your account was stolen! Please submit a ticket up to our account recovery team with your username/transaction ID to verify ownership: msft.it/6012kveiw ^TK
It sounds like you're not signing in with the correct credentials! If you're not able to access the account submit a ticket up to our account recovery team with the transaction ID and username: msft.it/6012kveTu ^TK
The best option is to submit a ticket up to our account recovery team! Make sure that you include your username/Transaction ID to best recover the account: msft.it/6014kvj9j ^TK
Is it saying that you can only use demo mode and have you migrated your account? If it's been longer than that let me know and we'll get you on over to the account team. ^TK