DTW Templates - Template not being created.

Dear Experts ,

I'm trying to update a UDT (Master Data) using DTW.

I tried to create a template by going to the Tepmlates in DTW  -> Customize Template ( Ctl+ M) -> select my UDT object -> right click on the object and create template from this structure. DTW reports that the template was created successfully but no template was created.

also when trying to update without the DTW template using A CSV file I'm getting the following :

no     Status                Key            Reason

1       Create Failed -      13          Cannot add rows to a MasterData type UserTable U_Test_Header

2     Updated Successfully 13     13U_Test_Header

Thanks in advance for  any help in this matter.

NC.