Try these troubleshooting methods if you cannot connect to the AT&T Home Base Manager.
INSTRUCTIONS & INFO
Make sure you are accessing the AT&T Home Base Manager via a device that is connected to the Wi-Fi or Ethernet connection of your Home Base.
Make sure you have entered the correct URL (http://att.homebase OR http://192.168.0.1) directly into your browser address field on your connected device. Note: Do not include “www” or “.com” when entering the URL.
If you have changed the login information and forgot it, you will need to restore the device to the factory default settings. Remove the bottom cover of your AT&T Home Base and using ballpoint pen, press and hold the RESET button for eight (8) seconds.