For a quick problem-solution reference, click on your listed device (below) for video conferencing issues.
Ensure you are using the right browser
For iPhone and iPad use Safari, for all other devices use Chrome
Are you using an iPad? Sound and video issues may be resolved simply by positioning your iPad in the landscape position, instead of portrait, and then refreshing your page .
Are you a an HP user? Some HP Computers have a Webcam Shutter Key to switch on and off Webcam Permissions. This is useful when having the issue No Video for the User only.
The above images are from the HP website for troubleshooting webcam issues https://support.hp.com/ca-en/document/c03430151
If you have a C-Slide, you will need to open the C-slide for your video conference.
Above is an image from https://www.amazon.ca/C-Slide-3228420-Webcam-Cover/dp/B00AZ639VG