Symptoms:
VMware vCenter 8.x
Queued tasks on the impacted ESXi host are preventing the FDM agent from being pushed successfully.
1. Verify there are no active backup's running in the backend.
2. Verify the tasks are hung on ESXi for a longer period of time.
3. Restart vpxd service to clear the queued tasks running on the ESXi host from vCenter UI:
root@vCenter [ ~ ]# service-control --restart vmware-vpxdSuccessfully restarted service vpxd
4. Re-configure vSphere HA for the specific host to push the fdm vib successfully..