Symptoms
An application fails to write to a site's document root, with an error similar to this one
The directory is not writable by the Web process
Trying to enable a WordPress plugin returns an error
Error: Permission denied
Error: Invalid URL was requested.
Opening the application in the browser shows access denied errors (for example, for the Umbraco application)
Server Error in '/' Application.
Access to the path 'C:Inetpubvhostsexample.comhttpdocsApp_DataTEMPPluginCacheumbraco-plugins.WIN-win.hash' is denied.The Additional write/modify permissions are disabled in Domains > example.com > Hosting Settings
Cause
The Plesk IIS and IIS application pool users for the site are missing full access rights are not granted.
Resolution
Log in to Plesk
Go to Domains > example.com > Hosting & DNS > Hosting
Enable Additional write/modify permissions
Press the OK button
To automatically enable this option for new domains, turn on Additional write/modify permissions management in Service Plans > Default > Permissions > Show more permissions.