Carrier Touch thermostat "A" will not connect to Orbi RBR850

The gateway is an 

Arris BGW210-700

12/21/2017

Software Version 4.28.7

Hardware Version 02001C0046004D

I've still not had a chance to put the Orbi into AP mode or try connecting to the gateway's WiFi. But since the thermostat works when connected to both a laptop and another WiFi access point, which both then go through the RBR850 and the gateway, it doesn't seem like there could be a problem with the gateway. If that were the case, the thermostat wouldn't work regardless of how it gets an IP address. It's getting a WiFi connection to the Orbi that's the problem. (I'll still try AP mode and the gateway's WiFi when I have a chance, but I have to do it when we can deal with the internet going on and off for a while.)

Interestingly, I got a voice mail message this morning from Netgear support. I had not contacted them. I just called them back with the case number they left me. After 40 minutes on the phone with three successive people I was told that my phone support had expired and that they could only help me if I paid for a support contract.

So, I suppose good that someone somewhere is watching, I assume this thread.

But really bush league to call someone offering support, then tell me to pay for it. And, likely they'd only lead me through everything I've already done. (If they want to troubleshoot this, maybe they should be paying me?)

It kind of fits my experience with Netgear products over the years: half-baked.