Not connecting to Wifi

I have tried everything iv reset my wifi,iv uninstalled the app reinstalled the app iv reset emo iv tried different networks i am on 2.4 ghz nothing i do gets him to connect i rang bt to check what ghz im on iv done everything i can i have had no problems what so ever until yesterday when i took him to my friends and connected him to her wifi and yes i have deleted her wifi can anyone please help