This started this morning and is persisting through logouts for these users across different hosts. Users are properly licensed and have been since day 1 of AVD back in July. We're running Enterprise Multi-Session on 16vCPU boxes with 64GB of Ram, 16 users per box.
Edit: It appears rolling the users vhdx profile back to Friday the 17th fixes the issue. Why that is even remotely the fix I don't know.
EDIT: This is worse today, and the people rolled back to Friday are still receiving the error.
No, I fixed it. Issue was after 5+ months the Azure Firewall just up and decided to start blocking the KMS service used to license the server despite having the WVD Service Tag being in use for that network. I have a ticket in with MSFT to figure out why this just happened out of the blue.