check whether the agent is running or not

ps -ef grep emagent

it will tell the location where the agent is running.
go to that location and run this command,

./emctl status agent
if it says "Agent is Running and Ready"
it means the agent is up and running.
If it is not running just give this command,
./emctl start agent
To stop the agent running, give this command,
./emctl stop agent