It’s not working on my iPad mini

It used to work. Now it doesn’t. I get a black screen, and get this message that auto exposure has timed and to try again if I try to take a photo. Of course the screen is black I am just testing, but I don’t understand why I get a black screen. All the controls are there. And yes I have the cover off the lens.

wallykateanne about LongExpo Pro - Tripod-free long exposure and slow shutter camera