I was having the same issue as you all experience, and have been looking for answers for a month now without luck. But I finally got it to work! I know it sounds ridiculous, but try just take a piece of cloth to clean the contact plate on your camera. Mine was looking perfectly new, without scratches or dirt, but somehow it started to work by just rubbing it for 2 sec.. :)
Uh, before you do that, try looking at how the histogram works: (it has essentially almost replaced the light meter for digital cameras.)
https://www.bhphotovideo.com/explora/photography/tips-and-solutions/how-read-your-cameras-histogram https://digital-photography-school.com/how-to-read-and-use-histograms/ https://www.cambridgeincolour.com/tutorials/histograms1.htm
Two ideas for getting to know shutter speed versus aperture...
1) Find something that you can get to move toward