Pull Server OS Upgrades

[RobBiddle]

I have a working DSC Pull Server running 2012R2 (Server Core if that makes a difference).
The Pull Server is configured via xDSCWebService
I'm using the latest xPSDesiredStateConfiguration (v. 9.1.0)
Clients are using v2 protocol (AgentID / Named Configurations).
Everything works perfectly on 2012R2.

I've attempted to do an in-place upgrade multiple times now to newer Windows OS (2016, 2019, 2022) and the result is always the same. Post upgrade the DSC configuration on the pull server still completes successfully without errors/warnings however clients can no longer connect. I get 'AgentID not found' errors. If I attempt to re-register it fails with an InternalServerError.

I've tried removing and re-adding DSC-Service and IIS post-upgrade to no avail.

What's the trick to getting xDSCWebService working on 2016+ OS?