Why can't I change category?
Mosets Tree performs a JSON request to your site to request for the list of categories when you change category by clicking on a category name. Here's the format of the URL Mosets Tree uses to perform the request:
where <yoursite> is your site's domain and XX is a category's ID.
When you can't change your category, the issue is typically caused by additional output that interfere with the JSON response. Removing these output should resolve the issue.
This is a sample JSON output from Mosets Tree's demo. It should starts with a opening square bracket and ends with a closing square bracket. It shouldn't have anything before and after those square brackets.