We are able to connect to the Audio bridge from the Dialer but the DTMF code (conference pass code) is not accepted.

We are able to connect to the Audio bridge from the Dialer but the DTMF code (conference pass code) is not accepted.

Goto VOIP>Audio>DTMF Relay and try changing the setting SIP Info, from Inband to Outband.  One of the options will work to enter DTMF tones.