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If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network - Apple Support

If you have a VPN App or profiles installed, or a security App such as Norton, these may be interfering with DHCP and preventing your device from obtaining a valid IP Address for your network. The resolution is relatively simple; may only need to temporarily disable or remove the Security App and/or VPN.

DHCP is frequently used to automatically obtain an IP Address from your WiFi Router. Until your iPad has a valid IP Address to connect to your network, you will not have an internet connection. Disabling or removing VPN and/or the offending security App should allow DHCP to operate normally - allowing connection to your network and the internet.

If this resolves your issue, the VPN and/or security App can be reinstated after the connectivity problem has been resolved.

Try restarting

https://support.apple.com/en-us/HT210631

Then try turning Wi-Fi on then off.

if it still isn’t working, contact Apple