First, let’s clarify terminology because "registration code" is ambiguous in pure Asterisk.
mysql -u root -p use asteriskcdr; update user set password_sha1 = SHA1('NEWpassword') where username = 'admin'; exit; asterisk password recovery registration code
Asterisk Password Recovery Registration Code: Everything You Need to Know including the registration code or password.
: You'll need to configure your SIP client (which could be a VoIP phone, a softphone, or another Asterisk server) with the correct details, including the registration code or password. asterisk password recovery registration code