has anyone else encountered this issue? i can see that they have been published to the server and that they are running and the cache exists. not sure what im missing?
ArcGIS Desktop Advanced 10.6.1
ArcGIS Server Standard 10.6.1
ArcGIS Image Server 10.6.1
I had a similar issue when I upgraded from 10.5 to 10.6.1.
You might want to check the API version in the Server Administrator Directory refer to thread below.
I have seen something like this due to mixed HTTPS and HTTP traffic.
Make sure you mandate SSL on both Portal and ArcGIS Server.
Don't worry if you just have self signed certs, it's just about aligning the protocols on the requests.