Oracle WebLogic application server (WLS) is quite a behemoth and usually works much better than e.g. OC4J which we previously had to use. But sometimes things don't go as they should and it gets stuck. Some time ago my managed Server was in "FORCE_SHUTTING_DOWN" state and when trying to restart it I got an error message.
"The server myServer is in an incompatible state.
Warning All of the servers selected are currently in a state which is incompatible with this operation or are not associated with a running Node Manager or you are not authorized to perform the action requested. No action will be performed."
Seems that this is a "common" problem with WebLogic Server and happens at least with 12c version which was also my case. The solution is to delete the "managed_server.state" file under your domain in "servers/managed_server/data/nodemanager/" where managed_server is your managed server's name.
So, stop everything, delete managed_server.state from your managed server folder and start everything (go to console to start your managed sever as it is SHUTDOWN).