If you have independent GPS modules for each screen, I would troubleshoot them independently. Let's just start with the one that is showing something in the counter.
First, do you see a huge red X on the map screen, or a flashing "?" in the middle?
In the serial setup screen, is it "GOOD SENTENCES" that is increasing or something else?
Do you have the SERIAL IN FUNCTION set to POS 1? Without this it will never use the input for anything.
Were you outside for more than 15 minutes? Your first lock after the GPS has been off for a very long time can take a while.
For the one with no counter- that sounds like a wiring issue. The counter should move no matter if they get a signal or not. Check that you have ~8V between the Orange and black wires. If you do, then make sure the grey wires make it to the harness. If all else fails, you may want to swap GPS modules between the screens.
