Start with basic WiFi troubleshooting - as detailed here:
If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network - Apple Support
Recommended settings for Wi-Fi routers and access points - Apple Support
Consider that your Router, to which you are attempting to connect, may be configured to require support for security features that are not supported by older versions of iOS. If you have an older iPad and your router is configured for WPA3 or WPA3/WPA2 mixed authentication, you will need to change this to WPA2 PSK(AES). Newer models of iPad support WPA3.
Some Mesh WiFi Routers are known to be troublesome in some circumstances.
If your WiFi has been set-up according to Apple’s recommended settings, WiFi and Internet connection difficulties are usually an indication that your device does not have a routable IP Address - your IP Address usually being assigned by DHCP. When this occurs, your iPad may only have a self-assigned link-local IP address that begins 169.254.x.x.
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 the WiFi network/hotspot to which you are attempting to connect. The resolution is usually simple; if installed, you may only need to temporarily disable or remove the Security App and/or VPN.
