We recently deployed Portal and federated with our existing ArcGIS Server sites. Our existing services have become "Map Image Services" and "Feature Layers" within the Portal Content. When I try to open a Map Image Service or a Feature Layer in the Portal Map Viewer, I get an error that says "The layer, [layer name], cannot be added to the map." I get the same message when I open a new Map Viewer and try to add the data from my content. I checked the console output, and only saw the following warnings (no errors):
[Deprecation] Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience.
DevTools failed to load SourceMap: Could not load content for https:// ... : HTTP error: status code 404, net::ERR_HTTP_RESPONSE_CODE_FAILURE
DevTools failed to load SourceMap: Could not load content for https:// ... : HTTP error: status code 404, net::ERR_HTTP_RESPONSE_CODE_FAILURE
DevTools failed to load SourceMap: Could not load content for chrome-extension: ... : HTTP error: status code 404, net::ERR_UNKNOWN_URL_SCHEME
[Violation] Added non-passive event listener to a scroll-blocking <some> event. Consider marking event handler as 'passive' to make the page more responsive. See <URL>
I am able to select "Add Layer from Web" and paste the REST endpoint from our rest/services directory, and the data loads without issues. We are on ArcGIS Enterprise 10.7.1, and most of our services were published using ArcMap 10.6.1. All of our sites are behind a proxy server, which we rely on to handle certificates.
If anyone has any insight, I would really appreciate it.