The docs say that you need to include this tag in the template:
[[ likeCssjs ]]
And if you're not loading JQuery yourself, you need this one instead:
[[ likeCssjs? &jsConnect=`true` ]]
If that doesn't work, that extra is an RC version from 2012, so my guess would be that it doesn't play well with more recent versions of MODX. I could be wrong.
