Does it say any errors as in Invalid place ID or maybe you did not enable 3rd party teleport in the game settings
also just a little optimization, you can put the service and place id as a local variable first so when the 30 seconds time is up, the script will declare these variables easily thus reducing a bit of script activity
local tpservice = game:GetService("TeleportService")
local PlaceIdtoteleportto = 6024797420
wait(30)
for i,players in pairs(game.Players:GetPlayers()) do
tpservice:Teleport(PlaceIdtoteleportto,players)
end