"Frozen Header That Changes as Visitors Scroll" only works in Preview

I followed the video tutorial on Youtube, and it works in preview, but the published site only shows the transparent header. Could anyone help me please?

Wix have their own tutorial as well as Nayeli (Code Queen) example or whoever video you are watching.

You can view it in your Wix Editor with al the elements setup and with all the code setup in your site tab too.

Thanks a ton for the reply! But sorry my issue remains. Do you mind to check my website as a contributor?