Analyze does not identify the compatible issue !!!! Which it should. Maybe is a bug need improvement.
ESRI never tell us that standard label engine will not compatible with arcgis online map viewer. You have to figure out on your own.
I have called esri customer service, they create a case with case number, however, they don't know what is wrong, don't know what to do, eventually they said they will escalate it to higher level team for further investigation.