Publish-AXReport : SSRS Deployment Error 'Domain/User' is not recognized

I faced this issue during deployment of all the default SSRS report when I was migrating the application from Development environment to UAT. The issue occurs due the previous AOS sessions that are present in the Table SysServerSessions table. This table will not be listed in the AOT and you will be able to access this table for viewing the records from SQL management studio, alternatively you can also create a dummy form and access the table from datasource.

There is no problem in deleting the records in this table as the records are automatically inserted by the AOS when AOS service starts up. 

Conclusion:- Turn off the AOS and clear the records from SysServerSessions table. Republish the SSRS reports it'll publish correctly.