What version of IDS software is running on 4215?
On VMS Machine open the IDS_EvsServer.log & IDS_Receiver.log files and see if there are any errors logged in there.
If all ok, then log on to the sensor. Do a show version and make sure all the processes are running fine.
If they are fine at the sensor end, then in the sensor console make sure that sensor indeed is producing alerts by 'Show events'
Cheers,
Rajesh