Hey Ryan! No resolution, I’m guessing it’s some new feature that been included in 4.17 (or 4.16), because I tried uploading a clean project from 4.17, and got the same message. But with a 4.15 clean project, it was uploaded successfuly.
I had to migrate the whole thing back to 4.15 and redo the blueprints, etc.
I tried disabling all of the online subsytem plugins and a whole bunch of other stuff, but nothing worked.