Hey, Faisal,
I just tested on Android, we currently have an issue with the right-hand panel, so audio is currently inaccessible from mobile portrait mode.
A work-around would be to tilt your device to landscape mode where the UI is a bit different. I was able to join in audio via the gear icon in landscape mode.
We are currently working on fixing this for the portrait view and will push an update to 'master'.
Audio on desktop landscape is also functional.
Thank you for reporting this.
Cheers,
Anton