It would be worth looking at the local rogue sensor log file to try an determine why it's doing that. Look for:
/<Sensor Install folder>/logs/rssensor_<host name>.log
Something else to consider is that sensors will be told to 'switch off' automatically if there are more than the required number on a given network segment for example.
Default =2 per subnet I believe, but that's adjustable. Maybe this network is covered by others already ?