HCX Admin Page > Configuration > Licensing and Activation ;
it fails with error as: Local licensing (Add-on) verification failed due to an invalid or expired key. See VMware KB 95336.

HCX
You cannot add new HCX Advanced key when another license exists.
Access HCX Admin Page > Configuration > Licensing and Activation
Edit the old HCX Advanced Key by clicking on three vertical dots and update the new license key.