obi-support2,
I've narrowed down the case where DTMF is currently failing (2289):
Telephone -> PAP2 -> (SP2) OBi110 (SP1:Google Voice) -> PSTN
This worked on 2103, fails on 2283, works on 2286, and fails on 2289.
These cases have no problem:
Telephone -> PAP2 -> (SP2) OBi110 (SP2:VoIP Provider) -> PSTN
Telephone -> PAP2 -> (SP2) OBi110 (SP2) -> SIP URI
Telephone -> PAP2 -> (SP2) OBi110 (PP) -> Echo Test