Thank you for reaching out for assistance, have you already tried clearing the cache of your camera application and restarting your device?
You can clear the cache using this pathway: Settings>Apps>Camera>Storage>Clear Cache and restart your device.
I have the same issue. I've only had the phone 4 days. I've tried all the fixes suggested and the only thing that worked was a factory reset 2 days ago. Now the only buttons I have at the top on the camera again are the flash & timer buttons. No settings gear or anything else. I don't want to keep doing a factory reset. Is the phone bad?