Dear Sirs,
I recently tried to upgrade one of my Yeelight YLXD01YL ceiling lights to the latest version
After the upgrade, the light worked until I powered it off.
After powering it on again, it is marked as offline in the app and I cannot use LAN control either.
I can see it registering on my WiFi network (I can ping its IP address) so I know it connects to my WiFi but I cannot telnet to it or use it in the app.
I have tried (several times) turning it off and on five times (reset) and connecting over Bluetooth using the app in order to get it working again. It pulsates a few times and the Bluetooth MAC address becomes visible in the app. However, a short while after I’ve selected what WiFi network it should connect to in the setup, it starts pulsating fast and the app times out.
I had one spare ceiling light as a replacement but when I upgraded the firmware, the same thing happened again. Now I have two unusable ceiling lights. 
Please help!