[George]

"won't install" doesn't tell us much.

Are you sure you are using the same email address as when you first purchased?

The registration code is case sensitive, are you sure it is being entered exactly as it appears?

You may have a corrupted download. Download again, and override existing file.

If those are correct, what kind of error messages are you getting?

If none of these quick fixes get you out of the jam, restore to a time prior to the upgrade, as Sam suggested.