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.