If the AA receives no tones, after three retries it should connect to the "no input" number, by default the Phone port. Upon answering that, if there is no audio, the problem is obviously unrelated to DTMF. If audio is ok, you can try pressing buttons at the calling end and listening for DTMF on the phone.
Why do you care about the GV path, since you already have the OBiTALK path working fine?
I know little about Jingle, but why do you care about the relay? Latency? Privacy? Because of subtle issues associated with NAT port translation, a relay approach is usually more reliable and robust. It also enables the provider to transcode, monitor quality, etc. For example, Vonage and Callcentric always proxy the media. Low cost providers often don't, mostly to economize on their bandwidth requirements.