[JAGENT] [ERROR] [OGGMON-20497] [com.goldengate.monitor.jagent.comm.ws.NotificationsCollector] [tid: StatusCollector] [ecid: ]
 Failed to get Status Information. RESTful Web Service might not be available.

 [JAGENT] [ERROR] [OGGMON-20494] [com.goldengate.monitor.jagent.comm.ws.NotificationsCollector] [tid: StatusCollector] [ecid:]
 Error occurred while registering the OGG process. Exception: [[
 source parameter must not be null 
]]
[JAGENT] [ERROR] [OGGMON-20609] [com.goldengate.monitor.jagent.comm.ws.ManagerService] [tid: MessageCollector] [ecid:]
 Unsuccessful connection response from Message Web Service. Query String: messages/last ; Response Code: 404 ; Response Message: Not Found
 [JAGENT] [ERROR] [OGGMON-20603] [com.goldengate.monitor.jagent.comm.ws.ManagerService] [tid: MessageCollector] [ecid:]
 RESTful Web Service with name messages/last has become unresponsive

Bug 23285087 is fixed in Oracle GoldenGate Monitor Agent (formerly jagent) 12.2.1.2.0

GGSCI (host) 8> create datastore
ERROR: Invalid command.

Patch 27848539: Oracle GoldenGate Monitor 12.2.1.2.181115 (PS2 BP4) (Cumulative)

 [JAGENT] [WARNING] [OGGMON-20027] [com.goldengate.monitor.jagent.config.impl.AgentInfoImpl] [tid: main] [ecid:]
 Property jmx.broker.port is not defined. Default value 5 559 will be used.
 Define this property with a value if the default is not what you want. 

OGG JAgent picks random ports instead of Static port (Doc ID 2346830.1)
Need to introduce the following parameters in Jagent config.properties file:
jmx.enable.remote.monitoring = true and
jmx.broker.port = < any valid port number>