I updated my Tab A (8") yesterday and after that it would not connect to my WiFi. It said authentication failed. Fortunately I had just bought a new Samsung Smartphone and had the same problem so I knew how to fix it.
It seems new Samsung devices use a random MAC address and this update made my tablet work that way. Since my network (WiFi and Ethernet) is locked down, only MAC addresses that I've approved are allowed. You have to change the setting so it does NOT randomize the MAC address. You have to go to your WiFi settings, advanced and change the MAC address type to TABLET MAC (instead of Randomized MAC).
Hope this helps people.