I'm sorry about the issue. Please press and hold both the Power (On / Off) button and the Homebutton (which is located right below the screen) together for at least 10 seconds, until the Apple logo appears, then wait a bit.
, then please go to Settings, General, Reset, Reset network settings, and confirm. Then go to Settings, Wi-Fi, then connect to your wi-fi/wireless network name and check.
Please let me know if there is still any issue. Thank you.