A problematic Internet connection is often due to incorrect wiring, improper settings or a service outage in your area. Perform a few troubleshooting procedures to diagnose and remedy problems with your Comcast Internet connection.
Visit the Comcast My Account website, sign in to your account and verify that there aren't any outages in your area. Also check to make sure you haven't missed any payments. Comcast may temporarily suspend your Internet service if your account is in arrears.
Unplug the power cable on the back of your Comcast modem or router. Wait at least one minute and then plug it back in again to re-establish your Internet connection. Make sure all other cords and cables are snugly inserted into the correct jacks. If you have any computers connected directly to the modem or router by LAN cables, unplug them and then plug them back in again.
Check Your Wi-Fi Connection
On a Mobile Device
Open the Settings app on your mobile device, choose Wi-Fi and then toggle the Wi-Fi switch off and back on to re-establish your connection. Select your Comcast Wi-Fi network on the list of available wireless networks and enter the password, if prompted.
On a Windows Computer
Swipe your mouse down to the lower-right corner of your Windows 8.1 computer screen, click Settings and then choose Network. Make sure Airplane Mode is turned off. Toggle the virtual Wi-Fi button off and then on again. Choose your Comcast Wi-Fi network on the list of available Wi-Fi networks and enter its password, if prompted.
Reset Your Wireless Gateway
If you still have connectivity issues, reset your Comcast modem or router. Locate the small slot on the back of the unit labeled "Reset." Insert a thin, pointy object into the Reset slot and press the button inside for two to five seconds. Release the button to restart the device. Wait for the device to finish resetting and then try again to access the Internet.
Do not press the Reset button for more than 15 seconds, as this will perform a factory reset, which erases all of your settings. Visit Comcast's Wireless Gateway Guides website to learn more about performing a factory reset.