Argument 1 missing or nil error with RemoteFunction?

Hello, Im trying to write a script where when you sit in the seat part of the car model I made, you get anchored down and it fires a remote function. But when I test it, in the output it says "Argument 1 missing or nil" and Im confused because this only happens when I Invoke a remote function. Here's the script

local Seat = game.Workspace.Jeep.Seat

Seat:GetPropertyChangedSignal("Occupant"):Connect(function()
    if Seat.Occupant ~= nil then
        wait(.5)
        local Char = Seat.Occupant.Parent
        Char["HumanoidRootPart"].Anchored = true
        if Char["HumanoidRootPart"].Anchored == true then

            game.ReplicatedStorage.Drive:InvokeClient()
        end
    end
end)