So this client says they never went on the ACA and they had insurance from their employer (1095-C shows that they were insured from January to August). However, the IRS is denying the return saying:

"The e-File database indicates that Form 8962 or a binary attachment with description containing "ACA Explanation" must be present in the return."

Is it possible that the gap from September to December has triggered something? Do I attach the 1095-C to the return as a PDF and then file it? The client says they never had insurance through the ACA.