Balance One Captive Portal - trouble with 'allowed client'

We are using a Balance One (firmware 6.2.2 build 2037) with Captive Portal (built-in splash page) for public WiFi via wireless access points in bridge mode. We have added individual MAC addresses to bypass the splash page and it works fine for computers that are directly connected to the access points. We have a customer using their own access point in station mode to receive the WiFi and pass it to their Peplink Balance30 router. It seems that when the customer is connected to their router they are always forced to the splash page, even though their MAC address is in the ‘allowed client’ list. We have even added both their access point MAC address and the Peplink router’s MAC address to the ‘allowed client’ list but our router still requires their computer to load the splash page. As soon as their computer disconnects from their router and connects directly to one of our wireless access points, then they are no longer required to load the splash page and they bypass it as intended. Any thoughts? Thank you for your help.


Please share a graphical network diagram for better understanding.

Thank you.