Thank you! But that's very strange ... that level has never failed in all my testing.
What it might be, though, is that there's a detail I might not have explained well enough: you need at least one block of (vertical) distance to actually "fall" on top of the other player. Otherwise, you just stand/walk on top of the other player. Does that help? I would love for you to be able to get past level 2 :)