I have the same problem. If you look in the (Xiaomi) Yeelight forums, there are many who have the same problem. For some it is only because they have not set up a 2.4GHz WLAN, the lamp can not handle 5GHz networks. I have tried to connect the lamp to my (2.4GHz) WLAN with the "Xiaomi Home App" as well as with the "Yeelight App": The lamp draws an IP (MAC address is visible in the DHCP client list of my router), but after some time the app reports that the lamp cannot connect, I should move closer to the router. I am standing right next to it and, as I said, it is obvious on the router that the lamp has obtained an IP.

Have you installed the Mi Home app? It worked for me without any problems.
FYI, it is not possible to connect the lamp directly to Google Home.
It is only possible to link the Mi Home app with Google Home.