Attempting to add a secure Web Feature Service (WFS) from a third-party Open Geospatial Consortium (OGC) server in Portal for ArcGIS and ArcGIS Online returns the error message:
Error: Item does not exist or is inaccessible.
Developer tools also return the error message:
Error: The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.
Note: A wildcard cannot be used when credentials are required, as it is too permissive, and defeats the purpose of requiring credentials. This is a security risk.
In the Web Feature Service, change the Access Control Origin from the wildcard '*' to include any origin requesting the service. Add the portal origin or any other domain to this location in the service.
Note: The method for applying the solution above can be different for each server, as it is done in a third-party server.