[Plugin: WP Marketplace – WordPress Shopping Cart System] 404 For Single Product Page

Try the default permalink. If it didnt work, there must be an issue with your theme. Try switching to a different theme.

Thanks for the quick reply! The default permalinks works! ??
However I can’t keep it like that. do you have any idea why this might be happening?

it might be a cause of your theme’s canonical redirect issue. If you are good in programming, then i think you can fix the issue. But if you cant, you better switch to another theme.

Yes I am a programmer. Thanks a lot for your help.
Btw, I’m using Twenty-Eleven theme. (default in wordpress) and it is making the problem.

So after around a week of frustration. I fixed this problem by simply calling: flush_rewrite_rules() after the new post type is added in the plugin. (it is specified by wordpress documentation to use it but for some reason you didn’t)
so in wpmarketplace/libs/install.php
the code for function wpmp_post_types should look like that:

function wpmp_post_types(){
    register_post_type("wpmarketplace",array(

            'labels' => array(
                'name' => __('Marketplace'),
                'singular_name' => __('Product'),
                'add_new' => __('Add Product'),
                'add_new_item' => __('Add New Product'),
                'edit_item' => __('Edit Product'),
                'new_item' => __('New Product'),
                'view_item' => __('View Product'),
                'search_items' => __('Search Product'),
                'not_found' =>  __('No product found'),
                'not_found_in_trash' => __('No product found in Trash'),
                'parent_item_colon' => ''
            ),
            'public' => true,
            'publicly_queryable' => true,
            'has_archive' => true,
            'show_ui' => true,
            'query_var' => true,
            'rewrite' => array('slug'=>'product','with_front'=>false),
            'capability_type' => 'post',
            'hierarchical' => false,
            'menu_icon' =>plugins_url().'/wpmarketplace/images/wpmp.png',
            'supports' => array('title','editor','author','excerpt','thumbnail','ptype','comments','custom-fields') ,
            'taxonomies' => array('ptype')

        )
    );     

    flush_rewrite_rules();
}