Dropper Elevator Not Moving Stuff Up?

I was following this guide to make a dropper elevator: https://youtu.be/PbwRrEKZpHA?si=-amt8qB8HdrHuI9m

However, it doesn't seem to be working, as the bottom dropper seems to just keep the items there. The comparator hooked to the two hoppers in the back seems to work, flicking back and forth, but the one next to the dropper does not seem to change at all.

Would greatly appreciate any help.