It's possible that the manager port is not open on the firewall for Agent and scheduling manager to communicate. Check the agent's receiver and transmitter logs for communication messages between the agent and scheduling manager, if the agent can receive the message from the manager and send massages back to the agent.
If the agent cannot connect with the manager, you can see exception like this in the agent's transmitter log;
07/25/2018 10:45:19.230 EDT-0400 5 TCP/IP Controller Plugin.Transmitter pool thread <Slow:1>.CybTargetHandlerChannelLogHelper.logConnectionAttempt[:75] - Attempting to open conversation to [email protected]:7507 using plain socket
07/25/2018 10:45:29.286 EDT-0400 1 TCP/IP Controller Plugin.Transmitter pool thread <Slow:1>.CybTargetHandlerChannel.constructConversation[:1190] - cybermation.library.communications.CybConversationException: connect timed out
If the agent receiver.log has no message entry from the scheduling manager, it means that manager cannot connect to the agent.
Make sure the agent and manager ports (default ports 7520 and 7507) are open on the firewall for agent and scheduling manager to communicate.
Note: Firewall can also be run locally on some servers such as Windows and Linux based systems. You'll want to check that as well as with your Network Administrators.
The agent and manager should be able to connect both ways.