Plesk shows 503 Service Unavailable: iisnode.dll failed to load The data is the error

Symptoms

• When loading Plesk the following error is displayed:

  CONFIG_TEXT: HTTP Error 503. The service is unavailable

• In Event Viewer > Windows Logs > Application the following error:

  CONFIG_TEXT: The Module DLL C:\\Program Files (x86)\\iisnode\\iisnode.dll failed to load. The data is the error.

• PleskControlPanel Application pool is stopped at IIS Manager > server > Application Pools

Cause

Plesk users psaadm and psacln do not have access to C:\\Program Files (x86)\\iisnode\\ directory by default.

Resolution

1. Connect to the server via RDP.

2. Add the following lines into the disksecurity.xml file which is stored in %plesk_dir%\\etc\\DiskSecurity\\ directory:

   CONFIG_TEXT: <!-- Program Files\\iisnode -->
   <Entry AccounType="1" Account="Psaadm" Path="{ProgramFiles}" SubPath="iisnode" AceFlags="ThisFolderSubfoldersAndFiles" AccessMask="Read" EntryFlags="0x40" />
   <Entry AccounType="1" Account="Psacln" Path="{ProgramFiles}" SubPath="iisnode" AceFlags="ThisFolderSubfoldersAndFiles" AccessMask="Read" EntryFlags="0x40" />

3. Open Plesk Reconfigurator by running the following command in cmd:

   C:\> "%plesk_dir%admin\bin\reconfigurator.exe"

4. Correct disk permissions:
   
   OR
   Repair Plesk Installation > tick checkbox Plesk File Security > Check.
   
   

5. Start Plesk Services Monitor:
   
   
   
6. Restart Plesk Management Service
   
7. Start PleskControlPanel application pool at IIS > server > Application Pools > PleskControlPanel > Start

If it does not solve the issue:

1. Back up IIS configuration file by running the following command in cmd:

   C:\> copy "%windir%\\System32\\inetsrv\\config\\applicationHost.config" "%windir%\\System32\\inetsrv\\config\\applicationHost.config.bak"

2. Remove iisnode module under IIS > Sites > PleskControlPanel > Module: