When vCenter Server is upgraded, new versions of the vCenter Server agents (vpxa) are installed on each ESXi host. If the host is also part of a VMware High Availability (HA) cluster, the HA agent (fdm) is also automatically upgraded to the newest vSphere 5.x version that is bundled with vCenter Server. After the HA agent is installed, the host is marked as "Reboot Required" before any further patches or upgrades can be installed.
Note: This issue will not be seen when upgrading from the above mentioned versions to a newer version. Upgrading to the above mentioned versions may still require the workaround below.
To work around this issue, reboot the host before attempting the Remediation:
Place the host into Maintenance Mode. Right-click the host and click Enter Maintenance Mode.
Reboot the host. Right-click the host and click Reboot.
Wait for the host to reconnect to vCenter Server.
In Update Manager, Scan the host again.
After the Scan, verify that the host shows as Noncompliant (red) instead of Incompatible (yellow).