In this case we would suggest you to try enabling and disabling the Guest wifi network on the surfboard central app then check on the devices if still the network name doesn't appear then you can try changing the security mode on the GUI of the modem then restart or power cycle modem for a minute then check for the guest network on your devices.

http://arris.force.com/consumers/articles/General_FAQs/SURFboard-Central-Web-Manager-Access

On the homepage of the GUI select Gateway > Connection > Wi-Fi > Edit Home 2.4 GHz

On the security mode click on the drop down arrow then select WPA2-PSK(AES) option and save it.

then power cycle the modem and the device then check for the guest network.

Thank you for the response … however, still no success.

I have:  deleted and recreated guest accounts; renamed guest accounts; rebooted the router after each change; and disabled the 5.0 network thinking the 2.4 would then show.

What is odd is that I can “see” the 5.0 guest account, but the 2.4 account NEVER shows.  Since that is the one that I need for my charger (2.4 GHz WPA2-PSK), I consider this as unsuccessful.  Might this be a router issue?  It’s still under warranty...

The 2.4G network is not visible on any of the devices, or only on a particular device?

I would suggest changing the Wi-Fi channels

http://arris.force.com/consumers/articles/General_FAQs/G34-G36-Changing-the-Wi-Fi-Channel

If the problem persists, after changing the Wi-Fi channels, I suggest to factory-resetting the modem:

http://arris.force.com/consumers/articles/General_FAQs/G34-G36-Factory-Reset

The 2.4GHz network was not visible on ANY device.  However, changing the channel did seem to solve it.  THANK YOU.

Channel 11 had 3 less devices than the next channel, so I used that one (vs 1 and 6).  If this conks out also/later, I’ll try using a channel that is totally free.  Thanks so much for the help.

Thank you so much for sharing your feedback.