3.5" 480x320 TFT interrupt pin not changing

I'm using this with a FireBeetle 2 over GDI cable. Attaching an interrupt to pin 16 (pin 16/D11 labeled as INT in FireBeetle 2 documentation) does nothing, and printing the status of pin 16 using digitalRead shows that it's held LOW no matter how much I touch the screen.
Touch function works fine other than the non-working interrupt pin.
Is there anything else I need to do to get INT pin working? Is pin 16 incorrect?