Hello. Step by step what helped me.
- I pulled out the battery.
- I brought the sensor to the gateway (it was white to the gateway).
- I inserted the battery.
- I pressed update.
- After pressing update, I immediately pressed the button on the sensor (so that it would blink for a while).
After that, the update took place, the update time was 30-40 minutes. The phone is on the same WiFi network and Bluetooth is turned on.