Att router 5G and 2.4G

By "online" do you me using Wi-Fi?  Strange use of the word.  I'd suggest using an Ethernet cable.

Let's get you connected back to your Wi-Fi, @craigsmith248!

Thank you for your help @JefferMC!

When signing in to the router using the address you provided, did you name your 2.4 GHZ channel a unique name that is easily identifiable? If your 5 GHz and 2.4GHz channel share the same name, then you have band steering enabled. This could possibly be the cause for your concern. Also, was the 2.4 GHz channel by chance disabled? If so, this could explain why it isn't working.

If all that checks out, you can always perform a factory reset. This will reset all gateway settings back to the information it originally had.

These are the steps to take:

1. Locate the Reset button on the rear of the gateway, located directly beside the power input.
2. Press and hold the button for at least 10 seconds. If you release the button sooner than 10 seconds, the gateway will reboot, but will not reset.
3. After releasing the button, wait until the device reboots and all the status lights on the gateway are lit. If the reboot was successful, the Broadband and Service status lights will be solid green.

Note: If you have changed your Wi-Fi network name (SSID), be sure to make note of it so you can re-apply it once you have completed the factory reset.

Let us know if this helps you gain access again!

CalebP, AT&T Community Specialist