I can explain, Essentials doesn't support command blocks mechanics like ex "@a, @p, @r", so you'll have to have to uninstall Essentials
and just use the normal bukkit TP command. I know I used to have Essentials but it didn't work on a adventure map, that's how I found the problem once. It's really anoying I must say, but I might contact the author and ask him to make support for the TP command.
I can't seem to get my command blocks working right. When i try the command /tell it works just fine, but with /tp nothing happens at all. I put in /tp @p 43 63 280 because that's the location i want to teleport to, but it doesn't do anything at all. I tried a lot of different things but i can only use the /tp command to teleport to other players. I tried this on a multiplayer server that has bukkit installed, not sure which plugins because it's not my server. I am in creative mode and i'm OP, so that can't be the problem.
My solution was simple. I took the commas out of it. So "/tp @p 40 500 29" instead of "/tp @p 40, 500, 29"
By the time I did that, it still wasn't working, and so I figured out that you don't put the decimals in the command. So if the coord is 400.9983 20.0000 35.99385 then you don't enter "/pt @p 400.9983 20.0000 35.99385" you just type "/tp @p 400 20 35" it does the same thing, but actually works.
Hope this helps, literally my first post ever on MC forums