Check the Error/HResult Code and follow this guide:
This problem occurs for one of the following reasons:
- You are using IIS 7.0 on a computer that is running Windows Vista. Additionally, you configure the Web site to use UNC Passthrough authentication to access a remote Universal Naming Convention (UNC) share.
The IIS_IUSRS group does not have the appropriate permissions for the ApplicationHost.config file, for the Web.config file, or for the virtual/application directories of IIS.
Do not configure the Web site to use UNC Passthrough authentication to access the remote UNC share. Instead, specify a user account that has the appropriate permissions to access the remote UNC share.
Grant the Read permission to the
IIS_IUSRS
group for theApplicationHost.config
file or for theWeb.config
file.
So in simple words, you need to:
Web.config
).IIS_IUSRS
group and confirm.