See below the settings within 3CX that amend the registration nonce.

NONCEEXPIRATION       

Defines nonce expiration time (seconds). By default it is 20 sec. After this time has passed since nonce issue — PBX will treat that nonce as expired and will force re-authentication (will issue 407 response with new nonce freshly generated).                

FORCEREAUTH

Forces PBX to re-request authentication if it has nonce that has already been used. If value = 1, PBX will force the check. If set to 0 – PBX will not check reuse of nonce.