The error message is not explicit when the second wifi interface doesn't exist.
In the wifi administration page, some old server (running 0.29.2) with only one wifi interface was showing errors message such as « No Wi-Fi device was found » and « No Wi-Fi available ».
This is not very explicit, since the logged in admin does know that there's a wifi interface (the hotspot he's actually connected to). The message could be more specific.