If the site is displaying something that says "comments disabled", then the problem is in your WordPress settings, not in the theme.
The "comments_template()" function is already included in the theme files and does not need to be added.
As you can see on the demo, the comments work fine:
http://www.shape5.com/demo/wp/ambient/sample-post-1/#commentsHello!
I?ve just created new article in the news and the button "Add a comment" appear!
But for all previous articles and blogs. There was no such button! But I found how to renew it via admin area.