Camera seems to disappear suddenly

I just activated this plugin yesterday. When testing it the first time in the afternoon, it seems to work okay except the the image on the camera looks awfully dark, very very dark. I opened window and even turn on my softbox light, it still look darker than normal.

But about several hours later in the evening after returning from running errands, when I clicked on the button, suddenly all I saw was a square black box with nothing else in it. No camera came on. Worse than that, my laptop (windows 10) camera suddenly showed only a pitch dark screen with no image came on, either.

Can’t figure out what happened.