My niece texted me and said that her iPhone didn't work on their wireless network, but worked fine on 4G/LTE. The rest of the family had no problems using the same Wi-Fi. When she tried to use something that needed an internet connection, the iPhone said there was no internet connection. The Settings app said it was connected to Wi-Fi.
This can sometimes happen. Usually it's pretty easy to fix problems with Wi-Fi in iOS. I wrote this list for my niece to try. It's the same with iPad as with iPhone. After each step, try if it's working. Usually one of the four first steps solves the problem.
Turn off Wi-Fi for five seconds and then back on again.
Go to Settings > Wi-Fi and toggle it off and on.
Reboot the device.
If your device has a physical Home button, press and hold it and the on/off button simultaneously until you see the Apple logo (about 10 seconds). If it doesn't have a physical Home button, push volume up, then volume down and then press and hold the on/off button until you see the Apple logo (about 10 seconds).
Delete the wireless network from your device and reconnect to it again.
Go to Settings > Wi-Fi and tap the ”i” to the right of the wireless network you are having problems with. Then tap Forget This Network.
Reset the device network settings. Note that this will make your device forget all wireless networks it has been connected to.
Go to Settings > General > Reset > Reset Network Settings.
Reset the device using an iCloud backup.
Go to Settings > General > Reset > Erase All Content and Settings. Choose to set it up using an iCloud backup after the reset.
Reset the device as a new device.
Go to Settings > General > Reset > Erase All Content and Settings. Choose to set it up as a new device after the reset.
Contact an Apple Store, or the store where you bought your device, and ask for help.
Please, comment below and let me know which step solved your problem.