I'm setting up a base deployment of ArcGIS Enterprise 10.7. To test things out, I've added one other person from my organization as a Viewer member to our Portal for ArcGIS. When this individual views a Map Image Layer (i.e., adds it to a web map) they have no issue. It appears on the web map with no issue. This Map Image Layer was created by publishing a shapefile to ArcGIS Server from ArcMap, and then sharing the content to Portal for ArcGIS (we've federated the server).
However, when this same user tries to view a Feature Layer in a web map, they get the error: "The layer, XXXXX, cannot be added to the map." The web map zooms to the extent of the feature layer, but it isn't added. This Feature Layer was added to Portal for ArcGIS by simply zipping a shapefile and then uploading it to Portal.
Both the Feature Layer and the Map Image Layer are shared to Everyone. And I'm able to add both to a web map with no issues as the Administrator. Is there a reason why the Viewer is only able to bring in the Map Image Layer and not the Feature Layer?