@Riffii 

Hi, normally after a successful factory reset, the default login password will be admin in lower case, or it will ask you to create a local password.

If not, please try reset it again and ensure it really resets to factory defaults successfully:

With the Mobile Wi-Fi powered on, open the back cover, use a pin to press and hold the Reset hole until you see "Power Off" on the screen, then TP-Link Logo, "Restoring" and "Succeed" will appear on the screen successively, which means the factory reset really works.