My countdown code isn't working?

Whenever it's time to countdown, it just says the round is already over. I'm not sure why, but it's quite annoying.

local maps = game.ServerStorage:FindFirstChild("Maps"):GetChildren()

local m = Instance.new("Message", workspace)

while wait(1) do
	m.Text = "Starting a new round!"
	wait(3)
	
	m.Text = "Choosing a random map..."
	wait(3)
	
	local chosenmap = maps[math.random(1, #maps)]
	chosenmap.Parent = workspace

	m.Text = "The map is " .. chosenmap.Name .. " by " .. chosenmap.Creator.Value .. "!"
	wait(3)
	
	m.Text = "Teleporting players..."
	wait(3)
	
	for i, v in pairs(game.Players:GetPlayers()) do
		if v.Character.Humanoid.Health > 0 and v ~= nil then
			local spawns = chosenmap:FindFirstChild("Spawns"):GetChildren()
			v.Character:MoveTo(spawns[i].Position)
		end
	end
	
	local roundtime = 60
	
	while roundtime > 0 do
		m.Text = "Time until next round " .. roundtime
		roundtime = roundtime - 1
	end
	
	m.Text = "The time is up!"
	wait(3)
	
	for i, v in pairs(game.Players:GetPlayers()) do
		if v.Character.Humanoid.Health > 0 and v ~= nil then
			v:LoadCharacter()
		end
	end
end

In line 30 you start the while loop but you don't have a wait(1) in there so basically it will instantly make roundtime = 0 because there is not wait in the loop

You did not add a "wait(1)" into the loop. Do this:

while roundtime > 0 do
        m.Text = "Time until next round " .. roundtime
        roundtime = roundtime - 1
wait(1)
    end