Interrupts Positiv egde ?

that is correct

Not complete correct. When you set interrupt on while signal is already true, he will be triggered at next rising edge. I.E. when going from FALSE to TRUE.

judging by the title and his comment, pretty sure he is on the right track (unless i missed something...)

interrupt need to be declared and active. only then it will sense the signal change and respond to rising edge (from false to true). so if it is already true, there is no reaction..

to sense falling edge, use NOT or compare signal with FALSE