HoneywellHome RTH6580WF Smart Thermostat Connection

​​​​Greetings!  FYI...I am posting this on behalf of my elderly mother, as I am the one trying to set up this thermostat for her.​​​​

​​​​I recently purchased the referenced thermostat and am trying to connect it to my new Xfinity internet/WiFi so that I can control the thermostat remotely.  When initially setting up the connection, I received an "E02" error code on the thermostat, which indicates an incorrect password.  That isn't possible, as I used the same password for this setup that I used to connect EVERY OTHER device in my household to this WiFi.​​​​

​​​​I discussed the issue with Honeywell, and the tech had me set up a Hotspot from my Android phone to see if the thermostat would login and connect to that Hotspot.  The thermostat did indeed connect immediately to that Hotspot!  So the issue was determined to be with the Gateway and how it might have some kind of setting that is blocking access from the thermostat and not allowing it to login to my WiFi.​​​​

​​​​I started thinking that maybe the thermostat was trying to connect to the 5GHz SSID by default when the thermostat is only compatible (per the box) to a 2.4GHz band.​​​​

​​​​So...I FINALLY found the user manual for my Gateway (Cisco Model DPC3941T) and found where/how to separate the 2.4GHz and 5GHz bands so they can be accessed individually.  I also manually added the MAC Address for the thermostat under the MAC Filter Setting and "pointed" the thermostat's MAC Address to the 2.4GHz SSID; the MAC Filtering Mode is set to "Allow-All".​​​​

​​​​Even with these settings, the thermostat continues to return an "E02" error code, indicating a "bad password".​​​​

​​​​So I am now seeking the help of the collective here.  Has ANYONE been successful in setting up a Honeywell WiFi thermostat with this (or similar) Xfinity Gateway???  Thanks in advance!!!​​​​

​​​​p.s. I installed this EXACT thermostat in my home, however the difference is my home equipment is a little different.  All the equipment I connect to Xfinity with is my own; a Cable Modem with a Netgear Nighthawk Router.​​​​

​*** UPDATE UPDATE ***​

​Had a "chat" with a couple of Xfinity reps.  The last one I chatted with recommended exchanging my existing Gateway/Modem to a newer model.  Am going to do that and see if that remedies my issue.......​

*** UPDATE UPDATE ***

Went to local Xfinity store and got another Gateway...same model as the old one.  I discovered during the online setup of the "new" box, the original WiFi password I had setup and WAS USING had an "illegal" character in it; an apostrophe.  So when setting up this "new" box, I eliminated the apostrophe from the password and tried connecting the thermostat again.  It kicked right off and connected successfully!!  So I guess the culprit was the "bad" password I was using with the illegal character.  Would have been nice to know that from "the get-go".  PROBLEM SOLVED!!!!