Seems the latest code is not compatible with Heroku.
"Heroku is a read-only deployment environment. Because of that, Rails
can't write all.css to /public/stylesheets/ and fails silently. The
stylesheet_link_tag still links to all.css as long as you use cache =>
true, so the quick fix is not to cache stylesheets on Heroku."
So, I would recommend removing this or fixing it to work on Heroku.
-steve