Why did the upgrade replace my previous license?

When you purchase an upgrade, it is still the same, single-user license you owned, it has just been upgraded to the new version. Therefore, purchasing an upgrade means it replaces the old version in your account with the new version at the upgrade rate. Once this occurs, you are no longer licensed to use the old version.

If you wish to own both the old version and the new version, you would need to purchase the latest version at full price.