These are VERY difficult to reinstall once they come out. I was a Husqvarna dealer for about 7 years. When I ran across that problem, I just replaced the cover. I don't know of any "tricks" or tools to reinstall it. Just a couple of screwdrivers and a lot of patience.
I'm sorry I couldn't be of more help. It's really a bad design. I don't expect any payment because I wasn't any help. Sorry again.