Having the following error trying to connect to the VMware vSphere Web Client?
503 Service Unavailable (Failed to connect to endpoint: [class Vmacore::Http::LocalServiceSpec:0000000002D9B4A0] _serverNamespace = /vsphere-client _isRedirect = false _port = 9090)
This is usually caused because the “VMware vSphere Web client” service has stopped unexpectedly or not started on boot. This service is and should be set to Automatic startup. To resolve the issue you need to start or restart it manually (on the vCenter Server), simply go to :
1. Control Panel > Administrative Tools > Services
(Or use the services.msc command)
2. Scroll down and locate “VMware vSphere Web client”
3. Verify the current state, right click and perform a Start or Restart operation.
It may take a little while before the WebUI come available. If an error is encountered I would make sure that the dependency services are started and also consult the EventViewer for pointers.
NOTE : I have observed this occasional behaviour on vCenter v5.5 and 6.0 as well.