Something is wrong with "FireClient"?

The error states that plr must be an object, even though when I print out the player before firing, it says my username. Why is this happening and how can I fix this? P.S. The if statement is inside of a modulescript function and fires every 1 second in a while true do loop.

    if seat:FindFirstChild("SeatWeld") and seat.SeatWeld.Part1.Parent.ClassName == "Model" then
        plr = game.Players:GetPlayerFromCharacter(seat.SeatWeld.Part1.Parent)
        print(plr)
        Sitting = true
        SitEvent:FireClient(plr,Sitting,seat) -- here
    else
        Sitting = nil
        SitEvent:FireClient(plr,Sitting,seat)
    end