My first question is: Are you testing this with someone at the gametable with you? A/V will not work without someone else at the table. Secondly, is the game you are a part of set up to allow A/V? A GM can turn off A/V entirely. If you are testing with someone else, can you please follow Steps 1-9
of our Solving A/V Issues checklist to see if
one of those components is causing the problem? We can only help if we
can recreate your issue, so it is important that you follow all the steps, even if you don't think the steps apply to your situation. You might have your helper try the steps too, to make sure the issue isn't on their end.