I have 2 brand new 3rd generation learning thermostats. I can connect either one independently to the app, but not both. Both are connected to the same wi-fi network, and both get data as a result. Both will setup independently, but once either is connected to the app, the other one will try to communicate with the first, and then timeout with a TD030 error. I spent over an hour on a chat with support. Several things they wanted me to try would not work ( ie. move the two closer together ... one has to be disconnected then and has no power so it resets ). They said the two must communicate with each other. WHY ? They are 20 feet apart, but each goes to a separate HVAC unit ( upstairs and downstairs ). The thermostats are working but it's pretty frustrating when they can't both be on the app at the same time. In the real world, with units install far apart in the same home, why would they possibly have one try to connet to the other ? If looking at wi-fi, both have no problem connecting to the LAN because they are both receiving a very solid signal. Tech support was doing a lot of guessing. I see a similar problem ( different error codes ) dating back over a year, so surely there is some documentation out there somewhere and a way to bypass this need to connect ( which isn't possible ).
I saw multiple threads on this, and no one had a solution. HOWEVER, I did figure out a solution. After hours working with Google <support>, and getting no where, I found my own option. The problem is that both thermostats must be near each other to pair, but how does one do that with no power ? It just doesn't work. They say take one off the wall and put it near the other. Is 3 inches close enough ? Without power, it isn't.
So here is a solution that does work, and apparently they know about it, but never share it ( according to a supervisor ) and it's not documented. I found it through my own experimentation.
Create a Home ( call it Downstairs ), install the thermostat, and pair it to the app. NOW, Create a second Home, call it Upstairs, install the other thermostat, and pair it. Then, to move between them, use the bar stack option on the top left corner of the app, select the floor, and you can fully control that thermostat. Yep, you can pair those remote sensors to them also ... it all works fine. It's not as convenient, and apparently Google simply assumes we are wealthy owners of two separate, nested, properties.
Give it a try if you're still suffering from this dilemna. I suggested the document it, or sell an extension cable that allows us to take the second thermostat close to the first one to pair it, but all they offered were "sorry for your incomvenience".
Sorry for the late response, but I wanted to drop in here to help.
I understand that thermostat issues can be confusing but I definitely wanted to stop by and see how I could help.
Just wanted to double check to see if you were still needing help on this? If so, what troubleshooting steps have you tried?
Please let me know.
Yes, I'm still having the problem. Dieter I did try ( again ) the iPad but that doesn't work either.
The chat tech told me to take one of the thermostats and put it near the other one. I tried it with both, one hooked up, the other flashing the little red light ... and of course the exact same error as in the original post.
When I talked to a supervisor, after finding my work around, he informed me that sometimes they won't pair, and I have to use two "Homes" like I found. Ok, that's annoying, but doable. Unfortunately once I did that, I then tried to hook them up to Alexa. Sadly, Alexa will only see one of them, even though they are both on the same LAN.
I bought Nest because everyone said they were the best, but the connectivity issues are not impressing me at all. I looked at a lot of options and this was the most expensive one. I would have loved to see it work.