Why is it if I'm making a video there is no sound

You may want to check this https://support.apple.com/en-us/HT203792 article out to troubleshoot your issue. If it still doesn't work you may need a repair.

If you are using screen recording then the sound is muted to prevent piracy.

I’ve the same issue. My volume is up and not set to silent. I’ve tested the microphone by recording a memo, and it works. However when using the Camera all to record, I hear a distorted sound and cracking, with my voice reduced to a whisper.