Failed Plesk upgrade to 11.5: failed to open stream: No such file or directory

Symptoms

Plesk upgrade to 11.5 fails. The following error is shown entering login and password at https://%plesk_hostname%:8443 :

CONFIG_TEXT: 500 Internal server error

Enabling display_errors in %plesk_dir%\\admin\\php.ini we get:

CONFIG_TEXT: PHP Warning: include_once(SB\\Application\\Api.php): failed to open stream: No such file or directory
Line: 95
File: D:\\Parallels\\Plesk\\admin\\plib\\Loader.php

Where %plesk_dir% is path to Plesk installation directory (e.g., C:\\Program Files (x86)\\Parallels\\Plesk ).

Cause

Missing files after failed upgrade.

Resolution

There is no required SB\Application\Api.php file under %plesk_dir%\\sb\\include\\ directory

It is possible to receive missing files from msi package from the autoinstaller repository and place it to required directory.

Use details from KB How to restore files from the plesk.msi package to get instructions for extracting files from msi package.

Alternatively, it is possible to copy missing files from the other server with the same OS and Plesk version.