When you did the reset of the tablet, did you opt to save personal stuff or not? If you did, that could be your problem, as anything on the device that was damaging (virus, malware, etc.) would still be on it. You would have to do a full "Hard Reset" to completely wipe and reset a device.
If that isn't the case, and you did do an actual "Hard Reset", then I would forget the info and restart the tablet. While the tablet restarts (turns off and back on) I would also reboot (turn off and back on) your modem/router. Once both are fully up and running then try re-entering the info.