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This happens if there is any issue with the iPad's firmware or with the router. To make sure this is not the issue with the iPad.
First we can reset your iPad and see if it works or not. Press and hold down the Power button and Home button at the same time until it shows the Apple logo. When you see the Apple logo, release the buttons and let it boot.
Then go to Settings > General > Reset and tap Reset All Settings. This will not delete anything from your iPad. It just resets some settings like WiFi, bluetooth etc.
You will have to reconnect your iPad to WiFi network after resetting all settings. Please let me know if that didn't work, so we can continue troubleshooting.
Remember, this is not my final answer. If my solutions didn't work please don't rate me bad or poor. Instead please reply back to me and I will continue to help you until we fix the problem or you are satisfied.
Did it work in the Apple Store ?
Also go to Settings and select WiFi. Does it recognize your WiFi network ?
I will not be able to call you as I'm also providing live support to other clients in here. But I will provide you support here without any additional charge until we sort thit out.