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.