You may need to restart the PBX services after the change to expedite the process. Of course this will only work if you have a 3CX FQDN.In Network Settings change your External IP Configuration from Static to Dynamic. Wait for the FQDN to update and then you can change it back.
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.