Kossel plus button not working

Hi all, I'm having problems with the LCD controller of my new kossel plus printer. It scrolls through the menu all ok but when you press down on the button it does nothing. I've swapped from the supplied reprap discount to the full graphics and also swapped over the ribbon cables but it hasn't made any difference. I'm running it on marlin 1.1.9 and did swap the controller in the config when I changed screens. Any ideas?

If you have a schematic for your LCD then you can check with ohm meter wither the button press will short the appropriate pins on the cable/connector. The pins of interest are identified from the schematic. Then you can check the pins.h file of your firmware to check that the proper MCU pin is assigned to the button functionality in the firmware.

Thanks for the reply. It actually turned out to be the soldering. Two of the points had soldering that was connecting them together when it shouldn't have. Removed the connecting piece and it worked straight away!