It looks fine to me, but where are you trying to click on it? From Dolphin it may just open a text editor. If you put it in ~/.local/share/applications it should appear in your application menu, and you can launch it from there.
A shot in the dark, but the only other thing I can think is to try Version=1.5 (the latest standard) or remove the Version line entirely (it’s optional). The full standard describes the file format.