Hi, I have a photon with an interrupt on pin A7. But when I try to programm it, it always sees it as high. I have checked with a multimeter and the voltagte on the pin is behaving as it should. My interrupt is set as an Input_Pullup and is set to trigger on a rise. The ISR for the interrupt is just incrementing a variable.
That behaviour seems not surprising when using INPUT_PULLUP as that is the job of the pull-up resistor 
You seem to have left out a crucial part in your “error description”:
How are you pulling the pin low to prepare for the pull-up to let it rise again?
I solved my problem actually (just forgot to remove my post…) In my ISR I had it write to another pin to see when the interrupt was activated but it seemed to cause the problem. After removing that line it worked.