I needed to reinstall PlanePlotter (actually on a different computer) but the receiver/antenna/etc was not changed.
After activation, I had a different Sharecode; now in the Top Sites section I have two listings, the dead one moving down the list and the new live one moving up. I think a way is needed to allow for situations where a Sharecode changes but it’s still the same ADS-B configuration.
It also appears that upgrading from Windows 8 to 8.1 will also force a PlanePlotter reinstallation which will cause a Sharecode change for those users as well.
That is normal and expected behavior for a sharecode change. Both sharecodes can be listed under your user account, and the stats for your user will properly reflect the sum of all sharecodes that you’ve registered. Once more than 30 days have passed (the period for our stats reporting), the old inactive sharecode will not be visible anymore.