I don't use ProConnect, so I can't comment on specifics.

But don't rely on the forms, rely on the information.  If it is "salary", enter it as a salary or a W-2.  Enter the Withholding.  Don't worry about it being on a 1042-S, but enter the pertinent information into the software.

If there is withholding, I would attach the 1042-S as an attachment.