Guys, I had an issue connecting my devices to yeelight app and after searching alot I found a solution that works for almost everybody.
1.Find an iphone and make sure its the latest ios.
2. Make sure you are connected to 2G Wi-Fi network.
3. Turn on your yeelight bulb and make sure you reset it.
4. Go to Apple Homekit and follow the instructions to add new devices. You can find the 8-digit setup code above the QR code on the bulb itself.
5. One you added the device on the application and its working go to Yeelight application and click on add device. On the page were you can select the light ( first page were you find all device picture) you find at the top “Add Accessories From Home” just click on it and follow instructions.
6. Once your done you will find the device on your main menu.
7. Now you can go use the Yeelight application on any mobile (Apple and Andriod) and you will find all your bulbs and devices.
Sorry for my bad english I hope this helps