Ya, that's a bad situation you have. My Timberline is almost 2 years old now. It was on original Gen2 firmware. About 9 months in, Traeger went to a new backend server (AWS I believe). They updated the grill's and a few of us were down for weeks but were able to finally reconnect. But there was a no return point that many who didn't update, and unsold grills in the pipeline couldn't update that were now orphaned.
The only recourse was a new controller with a high enough minimum firmware level to be able to connect to the "new" backend servers.
But assuming good firmware. The pairing sequence is critical. Having your phone connected to a known good 2.4ghz network, temporarily "forgetting" any auto connect 5ghz network so the phone does not inadvertently change networks during setup.
You initially connect your phone directly to the grill's built-in WiFi by scanning the QR code. Then the grill uses your phone to scan for networks, you pick your 2.4ghz network, the phone passes this info and login to the grill. The grill now severs the phone connection, logs directly onto your home network. Your phone now auto connects, hopefully, your home network. From now on, the phone connects INDIRECTLY to the grill via Traeger's servers. At this point you can connect your phone to any network you like.
You can verify the grill's wifi network connection and signal strength in the grill's settings under WiFi.
I've had 3 controllers for unrelated issues, all of them connected without issue, and some went thru updates once connected.
But in any case ensuring good WiFi signal to your grill area is important for reliable performance.
