Servers will turn grey in the SCOM console for a number of reasons but the main reason is the health service is no longer returning a heartbeat back to the SCOM console. When a monitored server is grey is means the server is no longer monitored and there is an issue. The issue needs to be resolved in order for the server to be turned back to normal state.
The first thing you need to do is the check the health service on the server in question.
Here you see the service is started. The Service name is “OpsMgr Health Service”, if the server is grey go ahead and restart the service. There is no harm in doing this and perhaps the health service will return the heartbeat to the RMS server and the monitored server will return to a normal state.
If the service restarts does not seem to be affective go ahead and view the local policy and make sure both “allow log on locally” and “allow log on through Terminal Services” are enabled for the user in question.
So you have done the first 2 steps and still the server remains grey. The next step is to stop the Health Service and go to the install location of the client on the monitored server. You see the path below and the files that are selected. Once the service is stopped, select all files in this directory and delete them, then restart the service.
These first 3 steps will take care of 90% of the issues you may encounter. If you still see your monitored server grey, check the certificates and make sure they are up to date, if they are make sure connectivity from the gateway is working correctly. Make sure connectivity from the monitored server to the gateway is good. If these items are good, then uninstall the client from the server and reinstall the client.
The MomAgent.MSI is the reinstall for the monitored server, uninstall this and then reinstall. You can get that information from the Operations Manager log. Make sure you look at the log before uninstalling since uninstalling the client will remove the log.
These actions should restore your monitored server. If they do not, seek help.