A user on a Polycom UA presses the Hold button.
The Polycom is configured with an MOH URI (RFC 7088). It sends a re-INVITE to reCon without SDP and with sip.rendering="no"
reCon responds correctly, sending 200 OK with an SDP offer.
Polycom is unable to contact the MOH server and simply sends an ACK to reCon with sip.rendering="no" and no SDP answer.
In this case, reCon should treat it as a remote hold without music and notify the application's ConversationManager.
InviteSession.cxx:1815 | Got Ack with no answer
InviteSession.cxx:2782 | Transition InviteSession::ReceivedReinviteSentOffer -> InviteSession::Connected
RemoteParticipant.cxx:2301 | onOfferRejected: handle=300, SipReq: ACK email@example.com:5062 tid=cbf8a95