Internet and wifi are working. Yeelight worked through my iPhone Xs Max app for a day, then went offline. Tried restarting (turning light on/off 5 times to get flashing color light), but still won’t link up.
Same issue on my end
delete the bulbs from the Yeelight app, delete the Yeelight app, then install Mi Home and set them up in that and it will all work again.
Have you upgraded to the newest version?