Hoo Boy ! Problem solved !!
When wiring a NJ International cross buck flasher for three rail you need three zones with each zone having electrically isolated common from the transformer/track power that is connected to the NJ board.
Southern approach, northern approach, and a crossing in the middle.
Track power can be used to power the NJ board.
Test WITH cars that have wheels NOT electrically isolated from the opposing wheel !!
DUH !
I was testing the circuitry with two rail cars.
When I rolled a Lionel three rail caboose over the circuit it worked.
I thought it had something to do with the caboose having a middle rail roller.
Nope.
It was the caboose wheels bridging the common allowing the flashers to work.
When I rolled an Atlas O two rail across, of course the wheels were insulated.
All three rail trucks now activate the flashers.
Test your circuits with three rail trucks.
Ahhhhhhh.
Now I can get a good night's sleep.
