Professor lectures for two hours online - on mute

A professor gave a two-hour online lecture but didn't know he was on mute. His microphone was off. None of his students could hear him. His lecture started well, but then the screen on his iPad froze. The video came back but the mic was off. The professor did not notice. Maybe it was because he used an iPad.

Students tried to contact their professor many times. They waved their arms and called his phone. The moment he understood his mic was off is now viral on the Internet. He looked shocked and stressed. He was upset because he wasted two hours of his students' time. He will redo the lecture.