UCM 6.1.5 , call flow is UCM -> SIP -> ACME SBC -> Verizon Broadworks SIP -> PSTN
Call is made from SCCP phone to an IVR with prompts, DTMF works. Put call on HOLD, then resume, now DTMF is no longer heard by IVR.
Verizon claims the ACK after HOLD has no SDP so IP=0.0.0.0 therefore no DTMF. I think I see UCM SDP go out with IP and with network-element for DTMF, but not sure. What could cause this problem with DTMF after resuming call ?