My game has bouncing balls that do a variety of things when clicked and a funnel with a gate you can open/close.
The first person that playtested it didn’t realize you could click the funnel buttons, so he just clicked on balls and rightfully got bored. I added a hint to the first level saying all you needed to do was open the gate.
The next two people then didn’t realize that the balls could be clicked. They just opened/closed the gate and rightfully got bored.
It’s hard to communicate what you intend for players to do without forcing them to do it in-game; I probably should’ve made a mandatory click this then click this kind of tutorial, but oh well.