The SIP URI [meeting_id]@<site>.webex.com, can be answered by a handset offering only voice [traditional phone type VoIP device], or a standards based SIP/H323 video endpoint.
WebEx "CMR" aka WebEx Meeting Center Video doesnt care either way, although it might make more sense to use 'computer audio' aka VoIP within a meeting so that user alignment between their video stream and audio streams are aligned so that active speaker switching works within a meeting---with a SIP VoIP only handset we'd switch the video to that user and then it would just be a blank/avatar screen/no active video--not an ideal experience.
So, given that your SIP handset isn't working, can you try unlocking the meeting first [if you havent] and removing the PIN code for attendees so that the 'phone' can dial directly into the already open/running meeting? [eliminates DTMF requirement to enter conf_id and/or PIN if you dial [meeting_id]@<site>.webex.com or [personal_room]@<site>.webex.com
If this still doesn't work, please open a support case with Cisco TAC
Thank you,
~Joe
