HELP!!! Creating an Xpress Sales Order from RMA Entry

Can someone please try to help me. When I go to create a new RMA entry in Sage 100, everything seems to work perfectly fine. But if I choose replace a product a customer ordered and I followed the help guide that said choose cross ship and I go to create an Xpress Sales Order and click yes to save changes I have made I get this message:  "You cannot create a sales order for cross-ship items because the Customer PO Number is required."

I'm not sure why that is happening. We do have PO# as a required field in our sales order entry process, could that be affecting this? I even tried to do this by unchecking the cross ship box but it does the same thing. I figure it has to be something fairly simple that I need to setup. Please post a response if you know how I can fix this. Thank You