The “no internet connection” warning usually indicates that your device does not have a routable IP Address - this usually being assigned by DHCP.
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.