Also receiving this error on one of my appliances in a two node F5 load balanced cluster in addition to the user portal not working for any user giving a session mismatch error in the horizon log (/opt/vmware/horizon/workspace/logs/horizon.log).  Have not found a root cause yet.  Only ran into issues when adding a second node in.

I have fixed the user portal issue.  Apparently you have to go into the Admin console and edit the Catalog settings and enable the new end user portal UI.  Kinda funky weird. but at least that piece seems to be working.

Still have the message service:

There was a problem with Messaging service.

Messaging Connection: Connection test failed

Hi guys,

I also have these problem regarding system diagnostic in a 2-node and a 3-node cluster.

This issue occurs with version 2.6 and the latest one 2.7.1.

Also seeing this error in a three node cluster on 2.8.

I also experienced the error in a three node cluster with version 2.8.

But the error disappeared after doing nothing for half an hour...

It looks like the IDM-nodes need some time to get fully in sync with the database.

I am using the SQL-server in this configuration.

The solution worked for a couple of hours. Then the error returned.

It doesn't seem to have degraded performance or integrity.

Messaging service is the Rabbitmq server. You can fix this by stopping and starting again in the right order:

Troubleshooting RabbitMQ Issues

Was able to build a 2.8 3-node cluster last week and get the messaging service happy.  I didnt the std install and clone, and then followed the steps on pages 7-9 of this whitepaper to get the elastisearch, rabbitmq, and ehcache services running smoothly

http://blogs.vmware.com/euc/2016/12/vmware-identity-manager-configuring-multiple-data-centers.html

The paper is mainly for a multi-datacenter design, but the steps can still be utilized for a single datacenter cluster for the most part.