Hello There,
Thanks for getting back to us. I have checked your site already. Your portfolio page is working find. I will explain to your what is happening in the portfolio page. Please know that the portfolio page will display 24 items by default. These 24 items will be regardless of its category. If you have more than 24 items, then you will be seeing page navigation at the end of the items. Clicking page 2 in the navigation will reveal to you the next 24 portfolio items. Now, the purpose of the portfolio filter is to filter out the items loaded on the page that belongs to the category. It does mean that clicking on the category will load the rest of the items because that is not the way how it works. It will only hide other items that does not below to the category you have selected on the filter.
Hope this explains it briefly.