Hi there! I understand you're having some trouble with the Sensi app on your iPhone. I'd be happy to help you resolve this issue. Can you provide a bit more detail about what specifically isn’t working? For instance, are you having trouble connecting the thermostat to the app, or is the app itself crashing or unresponsive?

Let’s start with some basic troubleshooting steps you can take:

1. Check Wi-Fi Connection:
Make sure your iPhone is connected to the same 2.4GHz Wi-Fi network that your Sensi thermostat is trying to connect to. If you're on a different network, that could be the source of the problem.

2. Force-Close the App:
Sometimes the app might just need a refresh. Try force-quitting the Sensi app by swiping it up or off the screen, then relaunch it to see if that helps.

3. Restart Your iPhone:
A simple restart can do wonders. Turn off your iPhone, wait a moment, and then turn it back on.

4. Reconnecting the Thermostat:
If your thermostat is offline or not connecting correctly, consider going to the thermostat and tapping the "Menu" option, then "Wi-Fi" to ensure it’s trying to connect to the right network.

5. Check for App Updates:
Ensure that the Sensi app is updated to the latest version. You can check this in the App Store.

If these steps don’t resolve the issue, let me know and we can try some more advanced troubleshooting or check if there are any server issues on Sensi’s end. How does that sound?