Yes the forum seems to be having some problems with attachments lately.
You can use "set flipped" in the player object's actions to flip the sprite vertically; mirrored is the same, but for horizontal.
Also, this flips, pixel for pixel, rather than @Knight05 's rotate solution. It depends how you want it to be flipped.
Edit: If you rotate, you will be facing the wrong direction, and will have to use mirror.