I understand what you are saying.
The checker is used to check new keys, not keys that are already registered in the database. You are right in what you are saying and it should check for new valid keys as well as existing keys in the database as this makes sense.
Can I suggest, Deactivating your key, click Reset, then enter your name and license key again. click Activate and then let me know how you get on. I will then check the database to see if it is all linked up.