Reason why my smartphone can't see ESSID?

I've got a nice new linksys wrt3200acm with openwrt installed. As far as I can tell there are no other problems with the router, apart from my phone not being able to 'see' the ESSID (and therefore not being able to connect to it). I've tried manually putting the ESSID on the phone, but still no wifi connection. I have 5GHz turned off, but I wouldn't have thought that it would have caused a problem with one device. For the record, the phone is a Wileyfox Swift 2X. TIA

If you've configured channels 12 or 13, try a lower one, as not all client devices allow using channels above 11.

Wireless is not enabled by default on an OpenWrt device. You must connect initially via wired Ethernet to configure and enable the WiFi.