Hi Ben59,
Is this a stand alone ESX host or a part of the VC? Is this screenshot taken when you are connected to the VC or directly to the host?
If this is from the VC, try taking a direct connection to the ESX host and check. If you are seeing the issue only from VC, then try disconnecting the host from the VC, connect it back and check.
If this is seen directly on the host (vSphere connection to the host) open an SSH connection to the host and do a services.sh restart and check
Regards
a