Found the solution:
The invoices had a negative value in the Age column. the way to fix it was do a datediff.

Dim currdate As Date = Date.Now
Dim begindate As Date = "1/1/1900"
Dim numdays As Integer = -1 * DateDiff(DateInterval.Day, begindate, currdate)
App.GetOverdueInvoices(numdays, duedate, invoicenum, custname, amount, custID, PostOrder, POA, transdate, begbal)