The FusionPBX responds with 480 Temporary Unavailable. Response example:
15/04 16.28.46.875 SIP/2.0 480 Temporarily Unavailable Call-ID: 62509696978349d6850850325c3ddd Via: SIP/2.0/TLS example.ringotel.co:5061;rport=36495;received=11.222.33.444;branch=z9hG4bK8f26dcd57bdfe53c From: "105" ;tag=45eac9b To: "18001111111" ;tag=8t17pgr558UDD CSeq: 22531 INVITE Max-Forwards: 70 Accept: application/sdp User-Agent: FreeSWITCH Supported: timer, path, replaces Reason: Q.850;cause=16;text="NORMAL_CLEARING" Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE Remote-Party-ID: "18001111111" ;privacy=off;screen=no;party=calling Allow-Events: talk, hold, conference, presence, as-feature-event, dialog, line-seize, call-info, sla, include-session-description, presence.winfo, message-summary, refer Content-Length: 0
Solution
Delete the organization’s domain from the FusionPBX ACL settings (Advanced → Access Controls).