I have tried : (Resolution 2 - done & Resolution 3 - can't find <add accessType="Allow" users="*" />)
To resolve this problem, use one of the following methods.
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 the ApplicationHost.config file or for the Web.config file. To do this, follow these steps:
In Windows Explorer, locate the folder that contains the ApplicationHost.config file that is associated with the Web site, or locate the virtual directories or the application directories that contain the Web.config file that is associated with the Web site.
Note The Web.config file may not be in the virtual directories or the application directories in IIS. Even in this situation, you need to follow these steps.
Right-click the folder that contains the ApplicationHost.config file, or right-click the virtual or application directories that may contain the Web.config file.
Click the Security tab, and then click Edit.
In the Enter the object names to select box, type computername\IIS_IUSRS, click Check Names, and then click OK.
Note Computername is a placeholder for the computer name.
Click to select the Read check box, and then click OK.
In the Properties dialog box for the folder, click OK.
Note Make sure the folder's properties are inherited by the ApplicationHost.config and Web.config files so that IIS_IUSRS has the Read permission for those files.
In the ApplicationHost.config file, delete the duplicate entry for the authorization rule. To do this, follow these steps:
Click Start, type Notepad in the Start Search box, right-click Notepad, and then click Run as administrator.
Note If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
On the File menu, click Open, type %windir%\System32\inetsrv\config\applicationHost.config in the File name box, and then click Open.
In the ApplicationHost.config file, delete the duplicate entry that resembles the following code.