Hi Yeelight team.
I have similar issue as guys above. But I have isolated it to some problem with my home wifi. (when I created hotspot on 1st phone and connected strip with 2nd phone it worked).
Do you have the list of potential settings which can influence connection? I am happy to work debug with you :).
Few info from my side:
Mi Account: 1755620339
Tried pair with: Yeelight iOS 3.1.10 (SE), Android 3.1.11 (S4), Mi Home iOS 4.7.1 (SE), Android 5.1.10 (s4)
Wifi Password Length: 13 characters
Note: other mi home smart gadgets (sensors, gateway, switch) works