I have Yeelight Arwen Ceiling Light 450S. It is connected to Wi-fi and I can control it via Apple Home Kit. It was also available in Yeelight app, but after one day it went offline there. Restarting app or Yeelight Ceiling Light does not help. I removed the light from the Yeelight app and I’m trying to add it again, but with no success. When I choose “Add Device” option then I can see the screen with a message “Scanning nearby Bluetooth devices…” and nothing shows up. When I choose an option “Add Accessories From Home” and then the lamp is invisible on the screen.
How it is possible that this light is visible in apple home app but not in the official Yeelight app? It is also offline in Xiaomi Home app.
I appreciate any help. 
