External joystick to control movement and homing

i am trying to connect an external joystick to my mpcnc using marlin and a MKS gen L


I have tried to connect it to AUX1 like shown, but i get nothing, usually when i plug my arduino into the computer, the TX light blinds and on the monitor i get the transmission showing.

But when i plug it into the board. the TX light never blinks. almost like it never opens the port.

Anyone have any idea how to get this to work.

I am following this information

I know the bloke mentioned it on here or the facebook group.