After upgrading our environment from ArcGIS Enterprise 10.9.1 to 11.5, we started experiencing an intermittent issue when adding a secured hosted feature layer from ArcGIS Online (not public) to our Portal for ArcGIS as a new item with stored credentials.
The item is successfully created and visible as a Feature Layer in Portal. However, when adding it to a web map or Experience Builder app, the layer sometimes loads correctly and sometimes fails to load with the following message: “The layer could not be added to the map.”
In the browser console we see:
Failed to load resource: the server responded with a status of 400 (Bad Request)
dojo.js:131 [esri.layers.support.fromPortalItem] #fromPortalItem() Failed to create layer from portal item
And in the Portal logs:
URL 'https://services9.arcgis.com/.../FeatureServer/2?f=json&' is not available: Unknown Host. services9.arcgis.com.
- DNS and firewall verified – services9.arcgis.com reachable from the server (HTTP 200 OK)
- Updated allowedProxyHosts for Portal – OK
Is this a known issue in ArcGIS Enterprise 11.3 / 11.5 related to the new proxy behavior when accessing secured AGOL layers with stored credentials?
Is there any workaround (configuration, CSP, proxy, or token refresh settings) that ensures stable communication between Portal and AGOL for such items?
Thank you in advance for any guidance.
