single portfolio view works properly on my test site.
Your single portfolio view is totally blank, this means there is a PHP fatal error, or memory exhaust, or PHP parse error. Please set your WP_DEBUG to true to look out for these errors.
Ignore any PHP notice, undefined index, warnings…etc.
Please post the error that you find here. ( Excluding warnings, undefined index, notices… etc ) I need to see the error message for clues.