If ELM327 WIFI successfully connected to your device — but fails to be recognized by the OBD App:
Force quit the app. With Android, use "Task Manager". With iOS, double-click the home button. Then launch the app again and see if it connects. If it still fails, then...
Within Apps settings, configure WIFI IP Address to 192.168.0.11 (or 192.168.0.10) and set Port to 35000. (Or number that sellers/manufacturers page has stated. Check their website where you bought WIFI ELM327.)
If ELM327 WIFI fails to connect to your Tablet/Phone:
Edit settings for the ELM327 WIFI signal. By default it will connect to DHCP settings. Set it to Static and enter the IP Address "192.168.0.11" (or 192.168.0.10) and Subnet Mask to "255.255.255.0". Connect again within the App.