Cannot turn on Wifi. MAC address unavailable I have an Android 4.0.4 tablet, Navon Platinum Explorer.

When I try to turn on wifi, the toggle button goes "off" after a few seconds automatically.
It doesnt even show the list of available networks.

In Wifi-Advanced, there is MAC Address - Unavailable.

The Wifi worked before doing a factory reset.
I also tried turning the table off and on, but it did not help.

What can I do to make the wifi work again?
I do not want to root the tablet.
I have no idea why,

but rebooting second time and trying to turn off/on the wifi icon on the homescreen several times did finally work.