I noticed that Prism Central wasn’t working ( 3 node cluster setup). Upon investigation it appeared I could ping all three nodes but not the VIP. In Prism Element I saw the message PE-PC Communication Failure in the Alerts section.
It appeared they had been powered off as part of a planned maintenance but whilst the nodes were powered back on the prism central cluster service was not restarted.
To start the cluster again log into any prism central vm and run: