There is no detection sound in the headphones despite them being switched on (and pressing the buttons generates an audible beep):

[FORUM XP]

1/ Check that you do not have a different coil selected in the Coil menu (see Headphones, Coil menu).

2/ The headphones have not yet been paired with the coil.
- Pair them (see Pairing headphones with a new coil).

3/ The coil’s serial number was changed inadvertently in the headphones and the headphones are no longer paired with the coil.
- Pair them (see Pairing headphones with a new coil).

There is no sound in the headphones when passing over a target and pressing the buttons generates no audible beep:

4/ The backphone is faulty.
- Change it, it is easy to replace (see Headphones, Replacement of the backphone).

5/ The earpiece is faulty, for example its keypad was poorly reconnected to the circuit after being dismounted, or the audio contacts are faulty.
- Contact your reseller or XP.