youp i was connected to 5ghz ;/
"Switch to precise location. "
Exactly this, after this I selected a WiFi network, and the name appeared in the box.
Without this, clicking the empty box it opens the WiFi Settings, but whatever you do (disconnect, reconnect, select a 2G network, enter a password with no wifi-network name in the box) nothing works.
The moment I went to the Yeelight settings and enabled Location Tracking and “precise” it worked… So you only need to give up your privacy and it works.
I had the same problem with the Wifi network not being read. You have to allow Yeelight and the government to follow you 100% accurate all the time, access all your data and then it works.