To resolve the blank screen issue you are experiencing with the Sensi app, please follow these steps:

1. Check Power Supply: Ensure that your Sensi thermostat is receiving adequate power. If it is hardwired, check the circuit breaker and ensure it’s in the ON position. Remove the thermostat from the wall to inspect if the backlight is lit. If not, there could be a power issue - learn more - learn more.

2. Reset the Thermostat: Perform a hard reset by pressing and holding the UP, DOWN, and FAN buttons simultaneously until the display goes blank and then reboots. This can help resolve software glitches that result in a blank screen - learn more.

3. Reinstall the App: Uninstall the Sensi app from your phone and then reinstall it from the app store. This can fix any app errors that might be causing the blank screen - learn more.

4. Check Wi-Fi Connection: Make sure that your phone is connected to the internet, as this is essential for the app to function properly. Power cycle your router and ensure it’s working correctly as well - learn more.

5. Device Compatibility: Ensure that your device meets the app’s requirements and that there are no updates pending for your operating system or the app itself.

6. Firmware Updates: If you can access the thermostat settings, check for and apply any firmware updates that may be available. Sometimes, blank screens can be attributed to outdated software - learn more.

If these steps do not resolve the blank screen issue, further technical support may be required. Consider reaching out directly to Sensi customer support for personalized assistance.