The ASP application works with an IIS-process 'user'. This user must have full read and write access.
The user name is IWAM_Machine Name. These rights should be given to the complete lpweb folder with all subfolders. The same is for the user IUSR_Machine name and user ASP.NET access. If you have a group IIS_WPG, add also full read and write access. If NETWORK SERVICE is available also add this user.
The user name is IUSR and the group name is IIS_IUSRS. If NETWORK SERVICE is available also add this user.
The necessary rights can not be configured in the IIS. They have to be configured for the file system.
•Login as administrator
•Open your file explorer
•Choose the lpweb folder
•Right-click and choose Properties
•On the "Directory Security" tab you can edit the access rights
•Set all rights to full access
•Click Advanced
•Select Inherit from parent the permission entries that apply to child objects
Also check the following settings and give read/write access to MSSharePointAppPool