IMPORTANT: Ensure your WAP server can also resolve the internal IP of your AD FS farm when querying your AD FS namespace. ...

IMPORTANT:  Ensure your WAP server can also resolve the internal IP of your AD FS farm when querying your AD FS namespace. If it can't, add an entry to the WAP server's HOSTS file. The HOSTS file is located in C:\windows\system32\drivers\etc\hosts (when opening, make sure you open it as an admin).