Reg: Participants accessing through mobile and low bandwidth

Team , We had hosted a Video conferencing with our colleagues from different region . We were 30 members. Unfortunately few of them could not join and if they joined they could not enter the room as we could not hear them or see their video . It was always blank for the other participants. However they could see us and hear us fully.

We are seeing this on multiple browsers and some of them had to move systems to join in. So we are not sure what the issue is

1 Is it due to the limit in number of participants
2 Is it network issue
3 isit Browser issue

No clue

Any guidance how to analyze this and any solution if any have faced this issue