Article ID: 128683, created on Apr 17, 2016, last review on Apr 17, 2016

  • Applies to:
  • Plesk Automation 11.5


  1. A websites running on IIS display the following error message:

    HTTP Error 503. The service is unavailable
  2. On attempt to get access to File Manager following error appears:

    Error: The unexpected HTTP code '503' was received on the HTTP request to the agent at ''.

    Where - IP address of IIS service node.

  3. In Event Viewer > Windows Logs > Application there is the following error:

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


Cause of such issue is that Plesk users psaadm and psacln do not have access to C:\Program Files (x86)\iisnode\ directory by default.


Change the NTFS permissions to the C:\Program Files (x86)\iisnode as follows:

  1. Disable inheritance and convert permissions from inherited to explicit.
  2. Set permissions to read for users psaadm and psacln.

Search Words

iisnode.dll failed to load

Service Unavailable HTTP Error 503. The service is unavailable.

iis hangs for one site

iis hangs for one customer

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