What DNS server is being used by the clients?
It should be using 192.168.1.1 as its DNS server. If you are using an external DNS server supplied directly to clients, you will need to add an IP bypass to the portal config for the DNS server IPs, or else the clients can't resolve DNS, which means they can't ever try to make the connection, let alone redirect.
That may not be your issue, but it's one of the most common.