Hi, I'm Pete. Welcome to JustAnswer! I'm reviewing your question now, and will post back with your reply ASAP.
Marcello, can you please confirm the make and model number of the handset and the collar?
Have you tried updating the firmware on both devices?
Which country did you buy the devices in?
If updating the software does not help, then "Disabled" is indicating that you are trying to use the device in a country for which the radio frequencies are not authorized.
It was possible to use some older collars in countries where they were not permitted for use, however the newer collars will work but only on authorised EU frequencies in EU.
I'm sorry if I was the bearer of bad news on this occasion, but my answer is correct -
the newer collars will work but only on authorised EU frequencies in EU.
It is illegal to use other frequencies.