I've finally figured out the mystery to this “use original charger that came with your phone" nightmare! After purchasing many, many, many new original Samsung chargers that have the fast charging feature. If you plug your cord into anything other than a fast charging charger (computer, battery pack, different wall charger) it's over! You can't. I had to buy a battery pack that offers fast charging option. If you have that original fast charging feature charger, never plug it into any charging device that doesn't have that as well. Pretty slick trick of Samsung tbh. I've purchased nearly 20 chargers between 3 phones that had this issue. There was no way all phones had the same charging problem. Since figuring this out…..no issues