Isotope Infinite Scroll is loading new content underneath previous content.

I followed this tutorial to achieve the effect.

My Problem:
When I scroll to the bottom of the page, where it should load “Next Page” contents, it ignores the isotope.js and loads “new content” underneath previous content.

There is a step in the tutorial I did not follow because I am not sure what the “textdomain” is. I understand that could be the problem so if you could enlighten me on what my “textdomain” is, I will appreciate it very much.

If you need any more information to help me figure this problem out, let me know. I appreciate any and all help.

Thank you!