How to connect phone using uart?

So I have been trying to connect samsung phones G920A to GCproKey using UART method. but its not working.
The phone cant be found always. I’m connecting z3X or Octo plus and connect uart cable to it to the phone and run the GCPro key.
never found it.
What shall I do to get it connected?
*#0*# not working. Enabling UART first and then look for it also not working. I think im missing something and need your help with this issue please.
Thank you