I got the same error message after I uploaded the files when I went to my admin section:

The www.popupparts.com page isn’t working

www.popupparts.com is currently unable to handle this request.
HTTP ERROR 500

Log file:
[02-Mar-2017 06:51:05 America/Chicago] PHP Fatal error: Call to undefined method AdminRequestSanitizer::addSanitizationGroup() in /xxxxxxxxx/admindirectory/includes/init_includes/overrides/init_sanitize.php on line 169