Hotspot - a single shared login and password

Hello I hope I can get assistance with this confusing matter.

We have established a basic Hotspot as instructed in the official documentation.
This hotspot is being used where one login and password is shared amongst all devices.

The first devices when connected are redirected to the captive portal for the login and password.
But after the first devices have connected other devices don’t get redirected to the captive portal, they can just start browsing.

I don’t really know what other information I can provide because it is a straight forward setup i.e. no advanced settings have been enabled and the firewall has not been altered or added to.

I really appreciate any help offered, thanks.

Based on the limited information you gave, all your clients are behind a NAT device, and therefore the Router only sees the other router. The first person signs in and that sign in the router they are connected to. In order for each individual person to have to sign in, you need each client to be on the same layer2 network as the hotspot.