Gateway reports no problems, settings in app appear correct, but SSID not broadcasting, no devices can connect to WiFi

About 4am this morning, my wife noticed nothing could connect to the WiFi, but the streaming box and phone box that are directly plugged in were still working.  After a while, WiFi came back, then went away.  This happened a few times, then WiFi just stayed bad.

We restarted the Gateway, waited for the light to go white, checked the app, it reported no problems and said we were getting 119% of our plan speed and the two hard-wired boxes were working, but no WiFi.

We unplugged the Gateway, waited a couple minutes, then plugged it back in, waited for the light to turn white, checked the app, same result.

I played with it a bit and turn off broadcasting SSID, saved the settings and restarted the gateway.  When it came up, I connected by manually adding the Wifi connection.

I turned broadcast SSID back on and the WiFi was now available and nearly all of our devices connected.  This lasted for 10-15 minutes, then WiFi went away again.

I called tech support and they said they were passing it up the chain and I would get a call back.  The call back 2.5 hrs later was an automated call asking if my issue was resolved.  I went to check the WiFi, since I wasn't near my computer when the call came through and it hung up before I could check.

I tried the Xfinity Assistant, hoping it would eventually connect me to live support, but it just went in circles asking for responses to the same prompts.

Why does the Gateway think everything is working and why can't I get the WiFi to broadcast properly, so my devices can connect to it?