✓ Accepted answer
You could use TweenPosition to Reposition it and make it slide across the screen:
game.Players.LocalPlayer.PlayerGui.ManaGui.ManaFrame:TweenPosition(UDim2.new(0, 331, 0, 226), 'Out', 'Quad', 1)
If you don't want to tween it, I think your problem could be that you're using pixels. You shouldn't use pixels to position GUIs because then the position will be different for different devices. Set the AnchorPoint of the GUI to 0.5, 0.5 and use the position relative to the screen size (i.e. (0.5, 0, 0.5, 0) positions it in the center of the screen.
This could also fix your issue (I think):
game.Players.LocalPlayer.PlayerGui.ManaGui.ManaFrame.Position = UDim2.new(0, 331, 0, 226)