Why isn't this Player script working?

First of all, .Died is not an event of the character model, it's an event of the humanoid.

I also think that the "Score" property of a "Team" object is not changed by using Team.Score.Value. I believe it's just Team.Score

If you have an IntValue named "Score", then that's a bad idea considering that there's already a property of "Team" that's "Score".

You also seem to be missing an end.

game.Players.PlayerAdded:connect(function(Player)
Player.CharacterAdded:connect(function(Char)
Char:WaitForChild("Humanoid").Died:connect(function()
if player.TeamColor == BrickColor.new("Camo") then --You could change this color to your own.
game.Teams.Sentinel.Score = game.Teams.Sentinel.Score + 1 
script.Parent.Text = game.Teams.Sentinel.Score.Value
--Assuming "Score" is a IntValue, then add `.Value` to it. This would give an error without it.

elseif player.TeamColor == BrickColor.new("Bright red") then --You could change this color to your own.
--What i've done is, what if the other team kills the other person? This would give them a score as well.
game.Teams.Atlas.Score = game.Teams.Atlas.Score + 1 
script.Parent.Parent.Atlas.Text = game.Teams.Atlas.Score
--Change TEAM2 to your other team, besides "Sentinel".
end
end)
end)
end)