We use full desktop clones with no profile management for a small group of users. This issue occurred for one of our users, regardless of any VDI desktop he accessed. Tried Win 10 1903 and 1809 along with Horizon Agent 7.7, 7.8, and 7.9, to no avail. His issue was due to the client he used to connect. For whatever reason, connecting via the latest Mac Desktop client 5.1.0 (13920831) as of this writing, resulted in this error message. Once he tried HTML5 access or the full Windows client via another computer, the issue went away.
In the event Log's search for Audit Failure and see if there is a message looking like "Unable to launch from Pool XXXX for user domain\username: No co-management availability for protocol PCoIP"
Next step, look at your connection servers and take a look at your CPU usage.
Lastly, add a few more vCPU to your Connection Server's. This worked for me to alleviate 99% of that issue. Though it still happen's from time to time, i know there is an open Engineering project internal to VMware on the issue.
We haven't seen this in a while. We ran into this a while back on 7.2/7.3 and it turned out to be a problem with the secure gateway process on the connection server causing this issue. I haven't seen this issue on 7.5.2