Unable to get ESP8266 wifi working

Should be fine. So I guess to get it to boot mode you ground GPIO0 with a resistor, apply power from Espruino, remove the resistor and flash.

In my case the board has v0.60.0 fw so just changing the module ESP8266WiFi_0v25 to ESP8266WiFi solved it for me.

Serial4.setup(115200, { rx: C11, tx : C10 });
var wifi = require("ESP8266WiFi_0v25").connect(Serial4, function() {
  //                ^^^^^^^^^^^^^^^^
  //                Use ESP8266WiFi here (and 9600 baud) if you have an ESP8266 with firmware older than 0.25
 ...
}