On my travels, I’ve had cause to sign into a couple of WiFi systems… and kept getting ‘this page can’t be loaded’ pages on my Mac when I should have got the sign in pages. Fortunately, I had another device which I could get online with and do some searching.
It sounds like it is a recognised problem with macOS ‘Mojave’ and some WiFi systems. The solution is to open a web browser and visit captive.apple.com. That loads the same page that the OS should bring up automatically and the login can be completed. Job done.
Mac – it just works… except when it needs a little helping hand.