I have seen this message before when there is no MAC address provided in the redirect from your wired/wireless to ClearPass Guest.
If you have control over the redirect URL, try adding '?mac=00:00:00:00:00:00' to the plain redirect URL. So for example if you configured the redirect URL now as https://guest.mycomp.com/guest/guest.php, change it to https://guest.mycomp.com/guest/guest.php?mac=00:00:00:00:00:00
If you can add the actual mac address to the redirect, that would be even better. And it is required if you switch access with Change of Authorizations, as ClearPass doesn't know where to trigger otherwise.
I'm not familiar with the WX5004, but it might be similar to the HP UWW product which has a TechNote on the support website. Search for UWW or go to the last one in the list.
If you get stuck, contact Aruba support (TAC) as they might have more guides or work with you live on the system to find how to make it work.