This Recordset is not updatable. (Error 3326)

Question

I migrated access tables to SQL and use the linked tables in a series of forms. Once option in the Main Form

updates fields from a table in a sub-form when I get the This Recordset is not updatable. (Error 3326) error.

I checked and the tables all have a set primary key.

Here's the Macro:

Private Sub Command104_Click()

Me!txtUseFee = [MRPCAdataCAWDMaster subform].Form.[txtUseFeeTotal]

Me!Units = [MRPCAdataCAWDMaster subform].Form.[txtUnitsTotal]

End Sub