Player needs to join brand new server after joining group?

I have been told players have not been getting their group perks after joining the group, and the script will only function after a brand new server is created.

--Give group perks
game.Players.PlayerAdded:Connect(function(newPlayer)
wait(1)   
	if newPlayer:IsInGroup(4071812) and newPlayer:WaitForChild("Data").GroupPerk.Value == false then                    
      newPlayer.leaderstats.Money.Value = newPlayer.leaderstats.Money.Value + 1000
	workspace:WaitForChild(newPlayer.Name).Humanoid.WalkSpeed = 20
	  newPlayer.Data.GroupPerk.Value = true    
	  
	newPlayer.CharacterAdded:Connect(function()
	  
	if newPlayer:IsInGroup(4071812) then
	local char = game.Workspace:WaitForChild(newPlayer.Name)
  
	workspace:WaitForChild(newPlayer.Name).Humanoid.WalkSpeed = 20
	else
		workspace:WaitForChild(newPlayer.Name).Humanoid.WalkSpeed = 16	
	end
	end)
	   end
	
end)

I wanted it to check every single time someone joins

Oddly enough, IsInGroup is cached on the server but not the client (according to the wiki). I would just tell the user to join a new server, or as oftenz suggested use Roblox's web API. Anything is better than getting the information from the client and using it on the server.