The key should definitely be working. There are many users, including this site, that use the key. The key is meant for sites with user-generated content, like this. Sites that use EasySocial generally should use it too, since they definitely have user generated content.
A few things to note:
* The System plugin is what replaces the 'tags'
* Try to use a simple render key with only numbers and letters. If you're using special characters, those may be the problem.
* If you have caching enabled, try disabling that.
From what I can tell above, it sounds like you got things going without the key. We'll gladly help get the key working as well, if necessary, just let me know if any of the suggestions above help.
Thanks,
Alex