Is there a way to make players cancollide false without them falling through the ground?

Add the following to a localscript and move it to StarterPlayerScripts in StarterPlayer. This should work unless you have something blocking it.

local charRegistry = {}

local function onCharacterAdded(char)
	local reg = {}
	
	local function registerChild(obj)
		if obj:IsA("BasePart") then
			reg[obj] = obj.Name
		end
	end
	
	for _,v in pairs(char:GetChildren()) do
		registerChild(v)
	end
	
	char.ChildAdded:connect(registerChild)
	charRegistry[char] = reg
end

local function onPlayerAdded(player)
	if player ~= game.Players.LocalPlayer then
		if player.Character then
			onCharacterAdded(player.Character)
		end
		player.CharacterAdded:connect(onCharacterAdded)
	end
end

for _,v in pairs(game.Players:GetPlayers()) do
	onPlayerAdded(v)
end

game.Players.PlayerAdded:connect(onPlayerAdded)
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

local rs = game:GetService("RunService")
local removeList

local function update()
	for char,reg in pairs(charRegistry) do
		if char:IsDescendantOf(game) then
			local torso = char:FindFirstChild("Torso")
			if torso and torso.CanCollide then
				-- Rename all the parts to BREAK.
				for part in pairs(reg) do
					part.Name = "BREAK"
				end
				-- Immediately switch back, and turn off collision.
				for part,name in pairs(reg) do
					part.Name = name
					part.CanCollide = false
				end
			end
		else
			if not removeList then
				removeList = {}
			end
			removeList[char] = true
		end
	end
	if removeList then
		for char in pairs(removeList) do
			charRegistry[char] = nil
		end
		removeList = nil
	end
end

rs.RenderStepped:connect(update)