Symptoms
The error message can be like:
unable to find valid certification path to requested target
backup has failed, unable to find identity of proxy. Server search certificate does not match
Cause
This is a known issue in 19.9 and 19.10.
Resolution
When vCenter certs are updated, we have to manually restart the vmdm service.
In addition, any external vProxies will need to be restarted to pick up the change in certificates.
Additional Information
If you need to check/update Cert, "ppcp certs -h" can be helpful