both of those files have become corrupted.
the paths to include files have been changed.
for example, in the index.php file, the path:
require_once('../PowerStore/PowerStore Files/webassist/themes/theme_open.php');
should be:
require_once('webassist/themes/theme_open.php');
this corruption may have happened in other files also.
I would recommend downloading a fresh copy of the power store files and re uploading them.