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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.

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