Just following up on a closed post
Device Fingerprint Rule Breaks after Migration to 5 (SBA)
I had the "Error communicating with the identity server" issue when using a fingerprint rule in a RISK policy.
Bizarrely it depended on the order of the rules, if the fingerprint rule is moved to the top of the list, then the error goes away and the rules all process as expected.
As usual, this may not be anyone elses issue, but worth mentioning in case it helps.
Shame the post was closed (unsolved).