Preproduction IDP error - La sessione non è più valida

[hello96]

Hi there!
I passed metadata validation a few days ago and I immediately started preproduction test, starting by pressing the button "cieid-cyberneid" that appeared, after configuring this provider, in the login page linked to the Admin Console:

When performing the authentication request towards the preproduction idp, I get the error page:

Here is a screen of the referenced attributes in my metadata:

and the details concerning the SAML Request performed:

What am I doing wrong? Any suggestion would be appreciated.

Thanks in advance!

[hello96]

In the end I tried to enable POST binding request instead of Redirect, I uploaded the newest metadata and it worked like a charm.