We are having more than 10 Dialogic Media GW 2000 in our worldwide corporate PBX and call center network, and we recently found that we are not getting GSM network early media where GSM network informs the users about mobile is unavailable, switch off or busy. We tried the below options
RFC 3960 Early Media Support -> Always ( Getting timeout message after a long silance), On Demand: Getting the ring first then Service Unavailable after few seconds.
Trying option "Continue Ringback on CN" from Voice Media Setting Send Early 183 Progress Response" but didn't make any different.
I also try to enable "ISDN Answer Supervision Enable" to yes.
The current firmware information is as below.
I also tried with Yealink phone T22p directly connected with GW but produce the same result.
We are not able to find any solution and start moving to SIP trunks where provider is supporting it. Please help.