Losing WiFi every 15 minutes and it's unsecured

I connected my laptop by ethernet to the gateway.  I verified the passwords and security are correct for wifi in the Xfinity software for the gateway.  The problem was still occuring.  The wifi drops out and there is still an open network.  I don't understand why I would have an open network with verification of passords and security WPA-2 enabled on both channels.  

I assume I need a new modem or I'm missing an obvious config setting somewhere to change network from open to secured.

The modem was originally installed by a contractor.  It worked until this event occurred recently. I called tech support but they said a possible software upgrade was causing it and that it wasn't a security risk to work on open wifi.  I disagree with that statement.

For the first problem. As a test, does a computer hardwired directly to the gateway device with an ethernet cable have the same problem ?

With this test, we are trying to isolate this from being either a WiFi-only problem or a problem with the general connection to the Comcast system which would of course affect both. It's a good first step of troubleshooting before we proceed any further.

What I meant by my question and the test was *does the hardwired connection simultaneously also drop out along with the WiFi* ?

The ethernet connection is good.  Signal stays on ....just wifi going out.