Why is the file not saved to the server?

Question

IIS

Hello!
Windows Server 2012 / IIS / MS SQL Server
After transferring the application to production hosting, files are not saved to the server.
An error pops up:

"1"
ExceptionMessage:"Ссылка на объект не указывает на экземпляр объекта."
ExceptionType:"System.NullReferenceException"
Message: "An error has occurred."
500 (Internal Server Error)

I suppose that the problem is in the rights of the user from which the application operates, but when I try to add a pool user to the "additional parameters" -> "credentials for accessing the physical path", it says "Invalid password specified. Please enter a new password."
What password does it ask for if no password has been set for this user? Maybe that's not the problem?

Answer 1

Add the user running the application pool to the access lists of the directory where the file is saved and set the access rights to "Read and modify", and also check the "replace all permission entries of the child object ......." checkbox in the section " Additionally"