Yeah, I was trying to swap some characters but all the mapping I made produced wrong things
I tried again on the PC with the Toshiba BT stack today, and after the second trial, the connection started and the device was registered correctly.
Now it works without problems even there.
Actually the "registration" seems just to be a white list to enable a specific service for a specific device, because in this interface you don't have a direct management of the paired devices (you can only remove them), and every service is accessible only after this "registration" thing.
For example if you want to activate HID control, BT Modem and BT Audio, you'll have to "register" 3 times the same device, ones for every service...