Z not homing (no replies)

I just upgraded an Ender 3, with a MKS Gen L v1.0 & a TFT touchscreen, to use an EZABL Pro.

I flashed the firmware, and updated the firmware on the touchscreen for auto leveling.
But when I try to home all axes, or just the Z, the Z moves up, from it's current position approx 5mm and stops.

What do I need to change in Marlin to fix this?