Server Error in '/' Application. Security Exception Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.
Exception Details: System.Security.SecurityException: Request for the permission of type 'System.Web.AspNetHostingPermission, System, Version=188.8.131.52, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.
changing the App pool identity to NetworkService / aspnet fixed it.
Additionally, enabling Load User Profile on the app pool also worked.