Error message when trying to activate marketpress

Hi - getting weird error messages when trying to activate marketpress
I have followed instructions here:
up to the point of installing marketpress - I have installed marketpress ecommerce via ftp, and can see it in my plugins directory. But when I try to either active in WP dashboard or network activate in WPMU dashboard I get:
Warning: require_once(/homepages/30/d343166253/htdocs/celticjewelrydesigners/wp-content/plugins/marketpress/marketpress-includes/constants.php): failed to open stream: No such file or directory in /homepages/30/d343166253/htdocs/celticjewelrydesigners/wp-content/plugins/marketpress
Fatal error: require_once(): Failed opening required '/homepages/30/d343166253/htdocs/celticjewelrydesigners/wp-content/plugins/marketpress/marketpress-includes/constants.php' (include_path='.:disappointed:usr/lib/php5.4') in /homepages/30/d343166253/htdocs/celticjewelrydesigners/wp-content/plugins/marketpress/marketpress.php on line 457

I did previously follow the instruction to add to my .htaccess and wp-config files. Can you advise?