After restarting your master your remote agents are in a service_down status and won't start any other way than by stopping/starting from the back end.
This seems to come from pulling the master out from under the remote agents. Before shutting down the Master the remote agents should always be put in a stopped status.
Please make sure all remote agents are stopped before shutting down the master. Please also add the following to the remote agent's $AW_HOME/site/awenv.ini file under the [default] section:
and restart the agent. This should allow you to restart the agent's from the GUI once the master is back up.