If the problem is that the asadmin start-agent command simply times out/uses a long time to start, and even possibly returning a filenotfoundexception. The problem could be as simple as a firewall blocking traffic to/from the master-node. A quick way to check it is to simply disable the FW.

Note that if the master-node does not see the node-agent status, it is also caused by FW-issues, fix the FW and then restart the node-agent(s), then it all should work like a charm!