Question about surrogate-agent for Acme 4600

Hi, I am not able to configure the SBC to send registrations to the trunk on behalf of the PBX. This is the surrogate-agent configured:

surrogate-agent

    register-host              voip.abc.com

    register-user              615444222

    description               Authentication on behalf of customer to trunk

    realm-id                Customer-C0268 --> this is the realm where PBX resides

    state                  enabled

    customer-host

    customer-next-hop            200.108.105.24 --> this is the trunk IP

    register-contact-host          65.100.17.34 --> this is the SBC sip-interface IP towards the trunk

    register-contact-user          615444222

    password                ****

    register-expires            600000

    replace-contact             disabled

    options

    route-to-registrar           enabled

    aor-count                1

    auth-user

    max-register-attempts          3

    register-retry-time           300

    count-start               1

    register-mode              automatic

    triggered-inactivity-interval      30

    triggered-oos-response         503

I have also enabled these settings under sip-config:

sip-config

    home-realm-id              Customer-C0268 --> this is the realm where PBX resides