All sketches in the part are uneditable because the "edit sketch" button that usually pops up when right clicking any sketch in tree has diasspeared. See screen shot. I've attached the part too. Maybe it works on your computer?

There is no way to add back in via right click>"customize menu" or "hide/show tree items.

The only thing I can think of is that the file has somehow become corrupt? It's a very simple part so I would be suprised if that were the problem.

Thanks in advance!