Thanks for reaching out — let's see what's going on.
A few questions: were there any recent changes or updates on your network or set up? Did you get any message before it happened? Also, is it the only device you can't control using your Google Home?
Could you try rebooting your Ewelink devices, Google Home speakers and routers to refresh the connection? Once done, try saying "OK Google, sync my devices? Let us know how it goes.