Had an annoying error today. Was updating an ESXi image for use with AutoDeploy. When I reinstalled the hosts they would not join vCenter. My workflow removes them from vCenter in the process, but they were unable to rejoin, and I could not add them manually either.
I got two error:
When selected the license in the add host wizard I got this error:
Cannot decode the licensed features on the host before it is added to vCenter Server. You might be unable to assign the selected license, because of unsupported features in use or some features might become unavailable after you assign the license.
I pushed through, but when the task reaches 100% it gave another error:
License file download from <servername> to vCenter Server failed due to exception: vmodl.fault.SecurityError.
Well to cut a long story short it turned out to be a time issue. Some of the serveres was not allowed to talk to the NTP servers. and their time had drifted. vCenter was located on one of these serveres, and its time was 5-6 minutes behind the ESXi servers that I was trying to join.
The NTP connection issue was corrected. Time was checked on all servers.
Hope this helps someone.