Teach First Wi-Fi public not showing splash page on Apple devices
You can tell users to navigate to the website http://neverssl.com or http://captive.apple.com/ upon connecting to the SSID if the splash page fails to load automatically for them.
Most new OS versions (both windows and mac) automatically checks with an http -based website when connecting to a splash page Wi-Fi option, so we are rarely having this issue now.
Unfortunately, I do not have any permanent solution, but to keep the neverssl.com website in mind for the users.