Nav13 R2 Installation Webservice Problem

Hello,
I NAV13 R2 installed as follows:
SQL Server -> own computer
First Middle Tiers Server -> own computer for the RTC User
Second Middle Tiers Server -> own computer for the programs which access via web to NAV.

Both Middle Tiers servers , Navision service running with the same domain user.
RTC works.
Only with the web service I have a problem. When I try to access the url "http://zsens82:7047/DynamicsNAV71/WS/services" it always comes the login query and
whatever I try, I can not I open page. But on the localhost it work´s.

What am I doing wrong here?
Where can i find documentation about navision installation on 3 Computer and for Web service.

thanks
stony