Guests can’t see the page
The page didn’t appear on an iPhone
Usually because the phone remembers joining before. Forget the network.
iPhones remember that they have already been signed in. Once that happens the sign-in window stops appearing, even though nothing is actually wrong.
Settings, then Wi-Fi. Tap the small i next to your network, then Forget This Network.
Turn Wi-Fi off for thirty seconds, then back on, and rejoin.
If it still does not appear, open Safari and go to neverssl.com.
Why neverssl.com? Almost every site a phone loads is encrypted, and an encrypted page cannot be redirected to a sign-in page. That site exists specifically to be unencrypted, so it forces the sign-in page to appear. It is the standard test across the whole industry.
If this did not solve it
Send us a message. Tell us the venue name and what you were doing when it went wrong, and a person will reply.