Problem with displaying 'Attach' button on custom post type

Hello!

Sorry if this problem was already resolved, I could not find the right topic (if it exists).

I have custom post type named ‘Downloads’ (I used a plugin to create a new one). In description it is said that the plugin supports custom post types, but in reality I cannot find it.

When I create a new (download) post, there’s no box with ‘Attach’ button.

I’ve even tried to create ‘my_attachments’ function in ‘functions.php’ and insert the right code to ‘single-downloads.php’, but it still doesn’t work.

Can someone please tell what is the problem?

Thank you in advance.

http://wordpress.org/extend/plugins/attachments/