Time to time, customers ask us about this warning. This is a by-design "benign" warning simply telling us a verification has been deferred to runtime. This can be ignored in most cases.
If you select your Application pool in IIS Manager and choose the basic settings, you will see following window:
Now if you click on "Test Settings…", you may see a yellow icon next to Authorization section and a corresponding warning message as follows:
Here is the warning details: The server is configured to use pass-through authentication with a built-in account to access the specified physical path. However, IIS Manager cannot verify whether the built-in account has access. Make sure that the application pool identity has Read access to the physical path. If this server is joined to a domain, and the application pool identity is NetworkService or LocalSystem, verify that <domain>\<computer_name>$ has Read access to the physical path. Then test these settings again.
This is just a warning, not Error. Path authorization couldn't be tested at configuration time, but it will be tested at runtime.