Last I made an Android Firmware Update with a Samsung GT-P7511. While the browser is connected to the Internet, but every page connects only with certificate errors and as a highlight the message when trying to connect to Playstore:
"can't establish a reliable data connection to server." This appears, and warnings, that the packet data option is not enabled, although you find yourself within a Wi-Fi, 3G, 4G or LTE network! Then simply check your date settings.
Often after a firmware update, the original manufacturing date is set again. If the correct date is set, then everything should work properly again. It worked perfectly for me.