The camera of my Lumia doesn't answer anymore, and the apps from the store puts a message: This cellphone doesn't have a camera or frontal camera. Anyone know a solution. I also reboot it and didn't work
At any rate, whether you're using W10 preview or WP8.1, you could try re-installing the OS using the Lumia Software Recovery Tool and connecting your phone to your PC.
If that doesn't work, then it could already be a hardware-level failure, something which may need a service center.