I am trying to publish a web layer that has a relationship class created in ArcGIS Pro, but I keep getting a warning that the related table is not in the map. The table is in the map, and I can add new records to the table using the Attributes pane.

I am not sure what I am doing wrong. I have remade the features and tables twice now, updated Pro, recreated the relationship class, etc.
Any help would be greatly appreciated.
- Miles