Since TS and MT are two independent systems it helps if you test tem as such.
On the MT server:
Test that you have a content processor set up to handle the extension type that you will be processing from TS.
Validate that this Content Processor contains all the fields you want to give to TeamSite. Make note of the exact spelling of the field names.
On the TS server:
If all of this together is working - you should be sucessful in the mechanics of tagging your content.