I've installed the pigpio library and so I decided to check it with a simple script that I hope it's right. I wanted to write a script whenever the PIR sensor detected motion. I've checked with multimeter if it was actually sending a trigger and it does, so I suppose there's a problem with software. In fact, regardless the script that may be wrong, even when I try to set the GPIO to an high state the multimeter still shows 0 V and even the example I found in the pigpio website (the Hall sensor one) doesn't work.
import pigpio
import time
pi = pigpio.pi()
pi.set_mode(25, pigpio.INPUT)
while pi.read (25) == 1:
"detection"
time.sleep (2)
Edit: sorry but I can't write properly the script here