Hello, I'll give you a solution that worked without even opening the phone nor doing any hard reset.
This problem started to happen me today. I observed that not only the led light was constantly on, I also found that the lens internal shutter cover was opened, like if I were taking a photo or video.
Remember that the led light is always on when you're recording a video and it's like this function would have been stuck or hanged and that's why you can't use any camera function while this annoying issue hapens.
But remember also that this is a phone with Windows on it, and how do you fix most of problems in Windows? yes! rebooting it. The problem here is that it also involved a hardware component, so in this case you need to turn it off. But how? the shutdown button doesn't really do a real shutdown... so? well the answer is clear letting the battery drain to make a real shutdown.
Before starting with "buah! I also tried that and it doesn't work" I will tell to all that people that it didn't worked for you because you really didn't drained the battery completelly to 0%.
When you discharge this phone with this problem, it will go through some phases till it's completelly discharged:
- First phase: the phone is turned off but that light still remains. This is a proof that the battery still has some charge. You must continue discharging it by trying to power on again the phone constantly.
- Second phase: because of doing the manual discharge, you keep trying to power the phone constantly. It'll try to start vibrating, showing the operator logo and finally it will power off showing a red battery indicator. In this phase, the led light will get off after many startup trials.
- Third phase: in this phase the led backlight is off and the phone won't try to boot even if you press the power button some seconds, but if you try it about half an hour or an hour, the battery memory will give it enough power to let it try to boot again. You must keep trying to boot it each hour and after that hour the phone doesn't try to boot, leave it 1 half a day and try it again. Continue doing that till you see that leaving it a complete day without trying to boot and you see that even trying again doesn't try to boot... YOU GOT IT!!! the battery is completelly discharged.
Now, you can connect and charge the phone normally, the light won't keep on constantly.
To close the shutter camera cover, just open the camera app (yes, it'll work again) and close it. The lens cover will be closed.
And that's all folks!!! I hope it also work for you.