Attempt to connect failed: Passed value is not a function?

The issue here is purely do to lack of proper endings. If you note your first function (raiseone), it lacks an ending. There should be one ending to end the for-loop and one to end the function. Currently you only end the for-loop. That means the next function is created inside the first function, and the problem persists through this function too. And then you have a lot of ends at the bottom to catch up. Bad habit and certainly not what you aimed for!

The fix is simple - move the overflowing ends from the bottom to their respective positions.

debounce = false

function raiseone()
    for i= 1,71 do
    script.Parent.DoorOne.CFrame = script.Parent.DoorOne.CFrame + Vector3.new(0,0.1,0)
    wait(0.02)
    end
end

function raisetwo()
     for i= 1,71 do
           script.Parent.DoorTwo.CFrame = script.Parent.DoorTwo.CFrame + Vector3.new(0,0.1,0)
           wait(0.02)
     end
end

function onClick()
    if debounce == false then
        debounce = true
    game.Workspace.BarDoor.BarButton.BrickColor = BrickColor.Red()
    spawn(raiseone)
    spawn(raisetwo)
    wait(25)
    game.Workspace.BarDoor.BarButton.BrickColor = BrickColor.Green()
    debounce = false
    end
end

script.Parent.ClickDetector.MouseClick:connect(onClick)