ASP.NET is not authorized to access the requested resource when accessing temp folder

I have the same issue.

Made the following changes to fix the issue.

(1) I have gone to wwwroot folder. Right-click and security tab. Provided IISUSER to set read and write permission to the wwwroot folder.

(2) Changed the application pool to the separate pool and set identity to Application pool Identity.

a really simple fix to solve my issue, in IIS I had to right click on Application Pools and set .NET Framework V4 to Integrated rather than classic/

Another solution was to set the specific folder that was being accessed to read/write to the users that required it, this can be done by unique users or within an organization, a group of users