Skeleton farm not working!

We just updated our Minecraft servers and I’m playing on Minecraft 1.14.3 Java edition and I found a skeleton spawner on our map. Then I wanted to create a farm with that one block water then one block with sign kinda elevator so they get up high and fall down and die you guys know what I mean, the classic cheap farm.

But now my issue is, that this elevator thing doesn’t seem to work. The skeletons just won’t get up for some reason.

Is this because of Minecraft updates or is there anything else I can try? We can’t really downgrade our servers…