I noticed the same thing on the 1st cover I purchased and soon realized that the magnet built into the cover was not properly lined up with the iPad's sensor. You can easily tell by experimenting with some small magnets and determine exactly where the cover's magnet is. Another issue I noted was slack in the cover's spine. When you close the cover, the the cover's spine isn't tight against the iPad's left edge, the magnet (in the opposite corner) will not line up with the sensor in the iPad. I switched to a Fintie brand cover (I had good luck with their covers for prior iPads) for my new iPad Air 4 and theirs works perfectly. I sent the other cover I bought (from a different company.. I can't remember the brand now) back as I had the same issues as you. I'd suggest trying a Fintie brand cover and see how that works.