Element x network ? icon

[Philip_2848]

Hi. 

Im using element x and the network icon changes to ? icon
What is meaning of this icon? 
The network status icon changes to this icon every time some times later configuring the network.
I have to reset the whole device by unplugging the power cable and re configure the network again every time when the icon changes to ? icon.
And I can not enter network configuration mode once this icon appears.

How can I solve this issue?

Thanks