Maybe the USB cable or transformer is broken. Please check USB cable and transformer then try again.
Please check if the Wi-Fi is 2.4G (unable to Connect to 5Ghz Wi-Fi ), and please open SSID.
Please confirm if the Wi-Fi password is correct.
Wi-Fi router can not be found. Please check if the Wi-Fi router is too far away, or if there is too many wall to affect signal transmission, etc.