Please check the microphone and camera of the zoom firstMobile phone version:1. Before entering the zoom classroom, go to the zoom settings and click on “Meeting”.2. Turn on “Auto Connect Audio” and turn off “Automatically Call My Number”.3. After entering the zoom classroom, check to see if the microphone is muted at the bottom left, and remember to check if the sound is turned on at the top left.If the above settings are completed, you can start to test this link.If there're still any problems, please check the following steps.