This is my first time working with Portal so please excuse me.
I have published a feature layer through our ArcGIS Server with feature access enabled. I can view and edit the feature layer in Portal. However, if I add the REST URL in ArcGIS Online it recognizes the layer, but does not display the feature and the attribute table is empty. I have sharing in Portal set to Everyone.
What am I doing wrong?
Do the time stamps on those errors "Method failed... The parameter is incorrect" coincide times when you were trying to access the feature layer in AGOL?
What version of Enterprise are you running (e.g. 10.8.x, 10.7.x, etc.)?