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 your iPhone hotspot - or the WiFi network 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.
DHCP is frequently used to automatically obtain an IP Address. 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.
There is a also new privacy feature included within iOS/iPadOS14/15 that hides your physical MAC Address - and instead uses a randomly selected Private MAC Address. This feature can negatively impact reliability of WiFi network connections with some WiFi Routers. You can enabled/disable this feature on your iPhone/iPad individually for each configured WiFi Network.
More information about this new feature can be found here:
Use private Wi-Fi addresses in iOS 14, iPadOS 14 and watchOS 7 – Apple Support
