It is not so straighforward to change the database with 6.12 and up now. The data connection setting is in Configurations > File Cabinet > More options, but it cannot be changed after the file cabinet is created.
You will need to edit the File Cabinet Settings directly to change the connection name and GUID. Make sure to backup DWSYSTEM before doing that. After the change all services must be restarted along with an IISReset.
Also, did you copy over the DWSYS table? That must exist in the new database too.
Senior Director Support Americas