As per our investigation, FreeSWITCH (v1.10.2) does not take off the hold state when receiving SIP INVITE without SDP (RFC 6337).

It answers with 200 OK/SDP with a=recvonly (expecting a=sendrecv and taking off from the hold state).

After setting channel variable sip_unhold_nosdp=true,  FreeSWITCH starts sending correct 200 OK/SDP, but it does not restore the media stream (calling side hears MOH).

How to solve this problem?

--