There are a couple of troubleshooting items listed in the following article that may also help you with this issue.  For example, if you have a state listed in the 2017 client file, is that state also present in your 2018 program.

Failure During Proforma Processing or "Failed to transfer" When Attempting to Proforma Client: https://accountants-community.intuit.com/articles/1608229&src=lsccom