First, welcome to the Webflow community! The sections and divs are not showing because they are empty. In the designer you can see them because it’s easier to click on them, but basically they are empty. If you add a height or padding you will be able to see them in preview mode too.
Just had a quick look, the project is rather complicated in terms of the positioning elements & animation, so I wasn’t able to look at all these sections. It’s great that you’re experimenting with the interactions though, and I was to get the two elements I looked at visable on preview.
I forced a min height on the elements in question (see img)
I changed the background colour in your ‘while scrolling’ animation to make sure they were visible and was able to see them after this.
In regards to those sections, you will want to force a min height, without any height rules like (Min Height: 200px) you won’t be able to see those sections.
You can use padding, force a min height or just force a height all work.
