Missing Icon and cannot Activate My Copy

I received my copy about 20 Aug and it took about 3 hours to download. Since then I have had no problems with the software, my only problem has been trying to sync my new Honeycomb Yoke. However, the other day when I powered up my computer, I had lost the Flight Sim Icon. Looked in all the usual places but could not find it. I decided that the only alternative was to uninstall and reinstall. This I did yesterday afternoon but now I am in the position that when I have to re activate the software with Microsoft, it states that the activation code has already been used. Redeemed.
I have a reasonably high spec computer and am running Windows 10. Help!!!