I solved the problem of camera and flashlight missing on my Huwei P9. It was due to the loose connector that holds both devices pins inside the top part of the phone. It can happen after opening the phone to replace other parts, because you sometimes need to take away and put back this connection. It can also happen whent the phone falls, the connector gets loose. So you must ask for opening and attach again this connection. In my case we needed to do it several times before having it tight enough, otherwhy it would happen again after a few weeks. Luckily this part is easy to access.