Hi guys, thank you,
I solved with a re-installation.
Jayanta
I've checked the 1^ link and the trust level was set on full trust level (automatically I would say, since I never changed that).
2^, to be honest it sounded little chinese for me, I have asked for help, but still waiting.
Jonathan
I've tried with all the possible urls, same as before.
Than I tryied to reconfigure the portal and the link "https://webadaptor.domain.com/arcgis/webadaptor"
gave me "page not found"
If I can't access the web adaptor page I can't reconfigure. (see below, probably I made a mistake when I configured the first time.
Paul
I've uninstalled and reinstalled. Now it works.
One thing about it, I am on windows 2008 standard.
The webadaptor can't be installed twice (tried on Windows 8.1 and it worked, here I couldn't) I had to use this workaround: https://community.esri.com/thread/113961
I am quite sure I made a little mistake when I created the duplicate (probably I copied the sites after the registration of the WA with the server) that's why I could not access the sites via WA.
Can't install the 10.4 I don't have the minimum requirements.
A day, when I have time I will use the cookbook. I am curious to see how it works.
Thanks.