Per the VBA documentation Excel Worksheet Copy
, the source and destination have to use the same Excel application instantiation. It looks like you're using the "objArchive" instantiation for the destination and the "frmFoodPantry" instantiation for the source. I think if you changed objArchive to frmFoodPantry when you create the destinationWorkbook object, it would work.
Note that this is only documented in the VBA object model (as referenced). The C# Excel Interop documentation doesn't mention it but I strongly suspect that's what's causing your problem.