client ID manager startup.log can see below error
03-26-2021 18:53:41.885 ClientIDManagerStartup 7036 (0x1b7c) [RegTask] - Client is not registered. Sending registration request for 63e89b2f-1ebd-4f79-ab9d-d31d1c85529b7 ...
03-26-2021 18:53:45.682 ClientIDManagerStartup 7036 (0x1b7c) [RegTask] - Server rejected registration request: 3
At the same time if we look at MP_registration manager.log
03-26-2021 18:54:3.532 MP_RegistrationManager 27315(0x5AC4)
Rejecting the registration request because Agent Type is CD and registration hint is supplied.
SCCM setup to use HTTPS/PKI.
If we open the Control Panel Applet (Configuration Manager) I can see Client certificate: None
Here is the solution when we searched for the device in SCCM --> Devices and went to properties, it was showing its old unique Identifier but in Configuration Manager applet will show another unique identifier.
Delete the device from SCCM, then re-discover it from the AD system discovery agent.
Then clients will get registered and will show a unique Identifier on both the SCCM server and a client machine.