Hi Cristina,

> But I have another problem related to registration process. After REGISTER-
> 401 Unauthorized-REGISTER-200 OK, the IMS client sends the SUBSCRIBE
> message (for the "reg" event package subscription) to the S-CSCF, the latter
> replies with NOTIFY and the client correctly responds with 200 OK. In order to
> be notified on any change of registration state for the client, also the P-CSCF
> sends the SUBSCRIBE message to the S-CSCF, the S-CSCF sends a NOTIFY to
> the proxy but, instead of replying with 200 OK, the P-CSCF replies with 404-
> Not Here (like it doesn't recognize that the recipient of the NOTIFY in the
> Req-URI is the P-CSCF itself).
>
> Have you ever seen similar issue?

I have now spent some time to reproduce the issue.
First of all: I had to adapt module reg_mod.c in ims_registrar_pcscf, because it containes a hardcoded P-CSCF address:
        str pcscf_uri = str_init("sip:pcscf.ims.smilecoms.com:4060");
which is only valid for smilecoms.
Did you also change that?

Then I got exactly the same problem. I found that the P-CSCF config causes in the part "# Check for Subsequent requests:" a reject " sl_send_reply("404","Not here");"
I have doubts that this is correctly designed and have to dig deeper into the logic of the config-file.
Fact is: the NOTIFY request does not contain a Route header and as it not an ACK it goes straight to the reject.
Maybe any IMS expert can shed some light on this code as shown below:

        # Check for Subsequent requests:
        if (has_totag()) {
                # sequential request withing a dialog should
                # take the path determined by record-routing
                if (loose_route()) {
                        if ($route_uri =~ "sip:mo@.*") {
                                setflag(FLT_MO);
                        }
                        if(!isdsturiset()) {
                                handle_ruri_alias();
                        }
                        # RTP-Relay, if necessary
                        route(RTPPROXY);
                        t_relay();
                } else {
                        if ( is_method("ACK") ) {
                                if ( t_check_trans() ) {
                                        # no loose-route, but stateful ACK;
                                        # must be an ACK after a 487
                                        # or e.g. 404 from upstream server
                                        t_relay();
                                        exit;
                                } else {
                                        # ACK without matching transaction ... ignore and discard
                                        exit;
                                }
                        }
                        sl_send_reply("404","Not here");
                }
                exit;

BR Franz