New customer here. Opted for the easy connect/self set up. All was fine. Suddenly stopped working. Can’t find the network on any device. Support said modem is working fine. I don’t know what else to do! I don’t want to pay for a tech.

What modem/router are you using? Cox says the modem is online, and you cannot see your WiFi, means either the router was reset and the network name you are looking for  was changed, OR the WiFi could be turned off. Many Routers have the ability to turn off WiFi, and the press of a button could fix your issue. 

How about some information, make/modem of equipment, and then we can provide more help. LOTS of experience here between Bruce, WMO and myself. 

Does wired work? Can you log into the modem/gateway at 192.168.0.1?

Each device had successfully connected but then disconnected, or the devices can't connect after being shut down?

You may need to "forget" the previous network.  If this doesn't work, reset the network settings in each device.