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Make sure that the speakers are not muted.
If using a desktop ensure that speakers are set up on their computer and that the computer is able to access the speakers.
Check the “Output Device” in the Windows and Mac Settings. macOS Microphone & Webcam Troubleshooting Windows 10 Microphone & Webcam Troubleshooting
Test that the speakers are working by playing a with a Youtube Video with the sound turned on.
If they you still cannot hear the video, they you may have a software/hardware issue that we may not be able to solve.
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