No Wi-Fi Icon or you see the icon but cannot detect or connect to the Wi-Fi network?
How often does it happen?
Have you tried to reset it to facotry defaults and reconfigure it?
Is it a brand new device?

HiThe screen not show the icon and my devices not detect the wifi.Depends, onces per 5 ciycles turn on/off I try like wickey:i removed battery and reinstall battery not solved the problemreset factory from admin panel not solved the problemreset from button in back of device not solved the problemand finally i update device firmware again at current version and not solved the problem. I try with and without sim card, wifi in 2,5 and 5 ghz, in 4g pref/4g only/3G only, roaming on/off. All tries without sd card. I bought the device new on April and the wifi fails since June.When fails, only if i wait with the devive turn off, about 1 hour, often, not always, wifi works.