Troubleshoot pre-call test error "A camera was found, but it is not sending video data"

Objective

The objective is to complete the pre-call test without any error.

Make sure the camera is not used by another application.
Check whether two publishers are created or not and make sure they are not configured to use the same camera as the video stream source, else only the first will work.
Kill the existing publisher by closing all the browser tabs.
Reboot the device and open a new browser instance and directly run the Pre-call test.

For more information on the Pre-call test, you can refer to our article OpenTok-Pre-Call-test.