Start10 Upgrade Lic Key

I upgraded a Start8 license to Start10 awhile back on a machine I just had to rebuild due to a failed boot drive.  When I did that upgrade I didn't get a new Start10 product key so now I can't seem to authorize my license since the Start8 key doesn't work on my Start10 installation.  I have licenses of Start10 installed on a few computers but can't get this upgraded one to work.  Any solution to this?  Thx