Is this the first time that you are connecting this mobile phone on your Wi-Fi? If so, you can check the Wi-Fi password on the sticker at the back of your modem.
Here's an article that can help you on this: Forgotten Your Wi-Fi Password?
Feel free to let us know should you require additional assistance.
Please post a screen shot of the Wireless/Wi-Fi status of your Mobile there is a possibility that your mobile phone is not directly connect to your Wi-Fi network.
Try to forgot the Wi-Fi network and reconnect it.
Let us know how it will go, cheers!