Built-in camera problem

Hello,

My built-in camera on my macbook is not recognized by the computer. Camera is not identified in hardware either in camera or USB.

I tried sudo killall VDCAssistant at the Terminal. Nothing happened.

I reset SMC for many times. Nothing happened.

At last, i tried to reinstall macOS but it looked like recovery server is busy.

So i couldn't fix the problem.

Does anyone has any suggestion?