Go in to settings, then services, then down to Webserver. Make sure allow control of XBMC via http is checked. Note the port displayed under the check mark. If it is checked, is there a place in the app to put your MAC address? If so, go to system information, down to network and note all of the info on your connection and make sure it matches in the app.
If none of these options work, I would recommend having a look at this app. https://play.google.com/store/apps/details?id=org.leetzone.android.yatsewidgetfree&hl=en