Error "HTTP Error 503. The service is unavailable" appears while opening Paralels Plesk Panel.
The following error is in Windows Event Viewer > System log:
Application pool 'DefaultAppPool' is being automatically disabled due to a series of failures in the process(es) serving that application pool.
And the following error is in Windows Event Viewer > Application log:
The Module DLL 'C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\isapi\spnativerequestmodule.dll' could not be loaded due to a configuration problem. The current configuration only supports loading images built for a x86 processor architecture. The data field contains the error number. To learn more about this issue, including how to troubleshooting this kind of processor architecture mismatch error, see http://go.microsoft.com/fwlink/?LinkId=29349.
Parallels Plesk Panel application pool is working in 32-bit mode. Global (i.e. applied to all application sites on all application pools) ISAPI module
spnativerequestmodule.dll (SharePoint 2013) is a 64-bit application. Attempt to load 64-bit application on 32-bit application pool is not possible, which causes application pool to fail on start-up.
IIS 7.x can load global ISAPI modules conditionally, depending on application pool's settings:
Open Command Prompt (Start > Run > cmd.exe).
- Type these commands:
cd %systemroot%\system32\inetsrv appcmd.exe set config -section:system.webServer /globalModules /[name='SPNativeRequestModule'].preCondition:integratedMode,bitness64
- Restart Control Panel service using Parallels Plesk Panel Services Monitor.