If your guests are connected to the access point but are not seeing the splash page, it means that the device isn’t even reaching Fydelia and there can be a number of reasons:

1) Make sure DHCP range is very large (like /23 or even /22). iOS hangs on to expired IPs and won’t reconnect.  This is a very common reason and is easily resolved.

2) When you disable the guest portal in UniFi everything works fine connects to the internet, making it appear as a Fydelia issue.  VLANs have gone out of sync and a router/gateway reboot is necessary.  Rebooting the router forces the network to sync the VLAN settings and it will start working again

3) Check that UniFi hotspot settings didn’t switch away from External Captive Portal to vouchers or something else.  We have seen this many times and it’s not due to human intervention.  Possibly a firmware upgrade quirk with UniFi

4) Make sure you have no apple.com domains in the walled garden. The inability for a device to connect to apple.com is how the device knows to show the splash page

5) Regular weekly reboot of all APs (hopefully automated via a PoE Switch).  The CEO of Captini (Stephen) told me he implements this solution when they have this issue.

6) Slow internet connections. We’ve seen this issue when running on poor network speeds such as 4G routers with low bandwidth capability. iOS in particular can get fussy and not show a splash page

We hope that helps!