I found their response to it on the 5.10 release here V5.10 Problems | MASSO Community Forums
which points to onefinity here Elite Series Masso Default Machine Settings and looks to be exactly my problem, as well as what I hoped would be the answer, a settings file from onefinity.
That didn’t do it either.
I rolled back to 5.10, which is as far back as they offer now, and reloaded the above file and no error!!
So the answer is I should have waited.