Error #26: Variable type invalid when trying to post invoice

SOLVED

We've been trying to troubleshoot this for 2 days now and were informed that Error #26 is Scanco related but from multiple forum posts here, I'm seeing that it is not necessarily related to Scanco. 

Our accounting team is getting the message: 

Error #26: Variable type invalid

Program: SO_158SALESJOURNAL_UPD.PVC

Statement: 4531

Class: SO_SalesJournal_upd

Method: UdpateInvoice

At a total loss for where to look for this issue. We have successfully posted invoices this week, and these 4 invoices are all credit cards but we have successfully posted a credit card one so it seems to not be specific to that payment type.