FireServer can not be called from client. Why is this happening?

So for context im making a script that gives the player cash when hitting a part above a certain speed, i made it fire a RemoteEvent instead because i think that otherwise it would not be FE compatible but now i cant fire it because of the the error mentioned in the title. How do i fix this, and is the script FE compatible without the RemoteEvent?

script.Parent.Touched:connect(function(hit)
    if hit.Parent:FindFirstChild("Humanoid") then
        local plr = workspace[hit.Parent.Name] --Access character from workspace.
        local player = game.Players:GetPlayerFromCharacter(plr) --Access (plr)
        if player.Character:FindFirstChild("Humanoid").Sit == true and 			 
   player.Character:FindFirstChild("HumanoidRootPart").Velocity.Magnitude >= 100 then
		game.ReplicatedStorage.SpeedCameraCash:FireServer()
        end
    end
end)

The event listener:

game.ReplicatedStorage.SpeedCameraCash.OnServerEvent:Connect(function(plr)
	plr.leaderstats.Cash.Value = plr.leaderstats.Cash.Value + plr.Character.HumanoidRootPart.Velocity.Magnitude*5
end)