Still commenting on your initial question, you only can uninstall an agent if it has the services stopped (shutdown) performed from the Agents List in the Vontu console.
If you don’t know how the services got stopped, you should login in the machine using the windows safe mode, go to windows task manager and try to start the services again from there. Then and once the agent communicates again with the EPS/Vontu, perform the agent shutdown action on the agent. Then you should be ok to uninstall it.
If it still doesn’t work, as last resource you can contact Symantec and request the Agent Clean Wipe tool.
Regards,
M