I am also having some challenges with getting custom buttons to appear. Some will show up, some won't - they default to the zen-cart default buttons (I thought - so I copied over those files just to kludge a fix). Seems as though buttons get displayed all over the place - and I'm having lots of challenges figuring it all out.
Can you help?

www.shirts 4 bronies dot com /store (we haven't launched yet)