/etc/network/interfacesdoesn't work -- at least not if you do it the same way you do visible networks, perhaps.
/etc/network/interfacesand get it working.
iwconfig wlan0 essid YOUR_HIDDEN_NETWORK key s:YOUR_PASSWORD
Error for wireless request "Set Encode" (8B2A) : SET failed on device wlan0 ; Invalid argument.
iwconfigshould show you're connected to the ESSID, at least. Then run this to setup DHCP:
RTNETLINK answers: File exists, which I found I can ignore, as it seems to be saying you're overwriting your previous DHCP settings.
If you run, `iwconfig` you should see an ESSID and Access-Point etc and `ifconfig` should show you your IP.
Edit on Github!