You might be able to suppress the diagnostic ("Efile" menu>"efile support tools">"Disable efile error...") and efile it anyway.

Especially since this account worked for your client last year with no issues, it might be a new ghost critical diagnostic.

Also wanted to clarify and make sure you knew that this is only a peer user support forum.  For official tech support, calling Lacerte tech support is the only option. I know you said you already called and the agent wasn't helpful, and I'm sorry. Each agent is different, sometimes you get ones that "dig" into things more and find solutions. But my bet is they'd tell you to try suppressing the diagnostic like I described above.