ADFS - Service Unavaible over WAP

Hi,

We have a simple ADFS enviroment with a WAP in a DMZ and an internal ADFS server. Problem is that we are not able to access the Test-Signon-Page (adfs/ls/IdpInitiatedSignon.aspx) or published OWA over the WAP. Internally everything is working fine and also from the WAP I can access the internel ADFS Server with the Test-Signon-Page and OWA with ADFS without problems.

But from the internet over the WAP we are always getting:

Through WAP we are also publishing Exchange Activesync which is working without problems.

I dont see any events in the eventlog, also with tracelogs. I don't see anything interesting in Fiddler on the client.

Do you have any ideas?

Kind regards

Patrick