Lanham (eShip) E-Mail Error

Does anyone know what the cause of the following error is with Lanham’s E-Mail functionality?

We are getting this on Sales Credit Memos and BOLs. The Sales Order Confirmation E-Mails work perfectly.

This was occurring because the report I was using wasn’t designed to print credits. In fact there is no out-of-the-box report that prints credits from tables 36 and 37. The Credit print reports are designed to print posted sales credits and there is no Lanham email functionality to email posted credits.