Why isn't WalkSpeed changing?

Hello Developers,

I would be very grateful if you could help me with my most recent issue.

Basically, (in the code I have included), I fire a remoteEvent to the client, then change walkspeed, and then print a debug statement.

Both the print statements either side of the walkspeed line output correctly with no other errors in either the console in-game or output window in Roblox Studio.

I would be incredibly grateful if anyone could help me with this.

local slowInformBoostEvent = boostFolder:WaitForChild("SlowInform")
	
for index, player in pairs(game.Players:GetPlayers()) do
	if player.Status.Value == true then
		if player.Alive.Value == true then
			if player.Murderer.Value == false then
				slowInformBoostEvent:FireClient(player)
				player.Character.Humanoid.WalkSpeed = 4
				print("WalkSpeed should have changed!")
			end
		end
	end
end

Thanks,

Anthony

EDIT: Apologies, I've forgot to add some extra context which I imagine would be useful. This code snippet is inside of a function called executeSlowBoost(), so Players should indeed me in the game (sorry - my fault for not specifying). I have even printed the name of each player who's humanoid walkspeed I am changing (to verify I am indeed getting the correct players as expected). In case it matters, I'm using a server script.

I am really confused because I don't understand how this not working.

Side Note: When I join the game and try to run a command from the server console log:

workspace.[TESTPLAYERNAME].Humanoid.WalkSpeed = 4

This also doesn't produce any errors, HOWEVER it too does not work.