Check Your Computer's Speakers/Headset Can you hear the "ding" when you change the volume level in windows? Does the computer have speakers? Is the headset cord plugged into the correct jack? Is the speaker volume low or set to 0?
Check Your Computer's Microphone? Does the computer have a microphone? Is it plugged in correctly? Is the microphone muted? Are you sharing the wrong mic? Is there other audio software hijacking the mic? Is Skype hijacking the mic? Test your computer using the Windows Voice Recorder App on your computer. If this doesn't work, something is wrong with your computer.
Check your Browser A. Using Firefox go to https://hosted.owlts.com/browser/test A dialog box should appear in the upper left corner of the browser. If it does not appear automatically, click on the grey microphone icon. B. Be sure to select correct the proper microphone option. C. Check "Remember this decision" and Click "Allow"
Once the microphone is enabled, the microphone icon should turn from grey to red and you should have an icon at the top center of your screen.
Check your Firewall A much less likely problem is a Firewall issue between the server and the client.