6m gps not recognized by pixhawk

I have bought a pixhawk clone named pixhack 2.8.4
I’m trying to connect a ublx 6m gps with compas to this flight controller.
This gps works fine with apm 2.8 copter 3.2
The apm and and pixhack gps pinout are the same.
My problem is that mission planner says " no gps" when connected to pixhack .
Is there something to configure to make it work with pixhack ?

I have found a few clone makers confuse the marking of Tx and Rx for comms.
Sometimes they mean ‘connect the Tx here’ and others ‘this is Tx data out’.
Have you tried swapping the Tx and Rx lines?

Yes, same result
But the gps works on telem1 port
I thing the pixhack has a problem because i can’t power it with a power module and the safety button looks inoperant