To reboot an AT&T U-Verse modem, shut down the system, disconnect power supply to the router, wait for a brief period, and restore power supply. Then, wait for the lights on the modem to illuminate, and restart the system. If required, press the reset button on the Power Supply Unit, or disconnect the battery used as a power backup.
After shutting down the computer when rebooting the AT&T U-Verse modem, remove the power cord present at the rear side of the router. Ensure that the lights of the front panel remain switched off. If the lights remain switched on, it indicates that there is a battery installed for backup purposes. In such a case, disconnect the battery to allow the device to shut down fully.
Then, wait for a time period of 10 seconds, and plug the power cord into the router again. If a Power Supply Unit or a Home Network Hub supports the service, push the red-colored reset button located on one side of the Power Supply Unit downward. Look for the PSU in a closet or a garage close to an external wall. Avoid pressing the reset button for a period of over nine seconds, as this restores the default factory settings in the external unit.
Now, wait for a time period of two minutes or until the indicator lights on the U-Verse modem begin to blink. Finally, reboot the computer.