I suggest trying the beta Roll20 WebRTC. From over here : The Beta Roll20 WebRTC is now available on the live production servers.
It is not selected by default, you must enable it from the Settings
(gear) tab, under the "Video + Audio Chat Options". This thread is only
for the Beta WebRTC, which will eventually replace the existing chat
option. If you are having issues, please provide your: Operating System Browser and Version Description of the Issue WebRTC Debug Log (Click the "Download WebRTC Debug Log" button under the settings tab) Known Issues: On
first connect with mixed browsers (Firefox/Chrome). We're seeing that
calls are very stable once everyone is connected. The problem is that
calls are often failing to connect users from mixed browser calls. The
work around right now is to click the "Reconnect" button if a
peer-to-peer connection failed on the first try. Issues with
creating connections when users have mixed audio/video settings. I.E.
one user has audio only, another has audio and video, a third has video
only. Issues with creating connections when a user has
either no webcam and they're using a video option, or no mic and they're
using the audio option. Avatar sizing options not available to players when BETA WebRTC is not enabled. If you have issues with the Roll20 WebRTC, please post the information requested to the Roll20 WebRTC thread, linked to above.