ITMS 8.5 RU4 was installed on a Windows Server 2022 system and the RU4 pointfixes were installed and the SMP Console and all elements of it worked as needed.
When starting Symantec Installation Manager (SIM) to upgrade to ITMS 8.6 RU3 the following message was seen in SIM and some functionality did not work:
The current operating system is not supported for installation. For more information, refer to Platform Support Matrix.
NOTE: Confirmed that the items in BLUE in the above screenshot are disabled too as this is an unsupported state:
ITMS 8.5 RU4
Customer did an in-place upgrade of the Windows OS on a ITMS 8.5 RU4 server to Windows Server 2022 system which is an unsupported configuration as per the following documentation:
Notification Server and Workflow Server
NOTE: In-place updates of the OS on Notification Servers are not supported either per:
173110 Does the IT Management Suite (ITMS) support in-place upgrades of Microsoft operating systems?
Some options are:
Windows Server 2022 Support Statement
169641 How to move or migrate Management Agents from one Notification Server to another.