Database Username and Schema do not match

I am using ArcGIS 10.2.1 and SQL Server 2008 R2.

I need to migrate a SQL Server Enterprise Geodatabase from one server machine (and Instance) to another server machine (and Instance). Let's call them Database A and Database B. Database A is the original SQL Server Enterprise Database and contains all the data. Database B is the new SQL Server Enterprise Geodatabase that contains no data. I want to move or copy the Feature Classes/Datasets in Database A to Database B.

I have tried Import, Copy/Paste, Exporting Feature Classes to a File Geodatabase then importing them into Database B, nothing seems to work.

I keep getting the same error message which basically says "Database Username and Schema do not match".

Any ideas on how to do this?