I rooted my Samsung Galaxy Lite 3 7.0 ( SM-T110 ) with Kingroot app. I then started having problem signing into any account I I had. I looked at the serial # and was notice that things have been altered. I did a factory reset and unable to sign into any app on the tablet. Constantly getting the same message " can't establish a reliable connection to server." and running out of ideas after attempting numerous ways to fix the problem.
If you did the reset that keeps any of your personal data, apps, etc. on the device, then it would not have truly reset it. Additionally, you need to 'unroot' a device first. Then do a "Hard Reset" which will totally wipe it and restore it back to its settings prior to anything being installed. This should fix the issue.