I had a look at your page:
...and found the button code appears to be working normally there? Did you resolve the problem?
About all I could think of was that you may need to save the page directly from your WP posting editor's raw HTML view (rather than switching back to visual-design mode before you save).
Another possibility is that you may need to force-refresh your page in your browser after making changes, to make sure your browser loads the very latest version of your page fresh from the server, rather than showing you an earlier version of the page the browser had stored in its cache from a previous visit. Hold down the Ctrl key when you click Refresh to do a "no really, I mean it" full reload of the page in your browser. :^)