Can you try this and see it helps.
To resolve this error you will need to disable signature validation checking on your IaaS server.
You will need to modify the following files (make sure you make a backup copy first);
C:\Program Files (x86)\VMware\vCAC\Web API\Web.config
C:\Program Files (x86)\VMware\vCAC\Server\Model Manager Web\Web.config
C:\Program Files (x86)\VMware\vCAC\Server\Website\Web.config
Adding these lines;
add key=”DisableMessageSignatureCheck” value=”true”
add key=”DisableBodyHashCheck” value=”true”
add key=”DisableSAMLTokenSignatureCheck” value=”true”
***Note add “<" and "” at the beginning and end of each line
Restart all of your vRA servers.
Thanks
Kumaran