ASP.NET session has expired or could not be found -> Because the Session.SessionID changes (Reporting Services)

You are probably storing your session InProcess. Try changing it to session state server. You can find more details here.

I'm using report viewer 11.0.0; in your web config on system.web section, put the next configuration:

<sessionState timeout ="120" mode="InProc" cookieless="false" />

When you are generating the report (C# code bellow) in the reportviewer object change the KeepSessionAlive property to false and the AsynkRendering property to false, and that's all

        this.rvReporte.KeepSessionAlive = false;
        this.rvReporte.AsyncRendering = false;

(rvReporte) is a ReportViewer control located on my asp.net Form This solution work for me, i hope that work for other people.

Regards

<httpCookies httpOnlyCookies="false" requireSSL="false"/>

Solved the problem. Thanks to : http://www.c-sharpcorner.com/Blogs/8786/reportviewer-Asp-Net-session-has-expired.aspx