IIS runs websites by using application pools. Application pools process requests based on the default or customized settings. Application pool identity is one of these settings. It is the account that runs worker processes and perform corresponding tasks.
While trying to set a custom account as app pool identity, you may run into this issue: “Value does not fall within the expected range“. This error occurs if you are specifying a custom account (not using any predefined accounts such as NetworkService).
There was an error while performing this operation. Details: Value does not fall within the expected range.
Custom application pool identity window in IIS Manager has only fundamental validations such as empty field check and password match check. Therefore the error message above does not always lead to a solution.
It is possible that there is something simple such as a formatting issue in the config files is causing this issue. Try the steps below first:
Check the applicationHost.config file (C:\Windows\System32\inetsrv\Config) for any formatting issues
Try to find a clean copy of applicationHost.config and replace it with the existing one
Restart Windows Process Activation Service (Reference)
Restart IIS Manager
net stop was /y
net start w3svc
If the issue still occurs:
Create a new application pool and try change its application pool identity
Make sure to open IIS Manager as a local or domain administrator
Check Event Viewer for more details about the error message