The same message appears for:

Overzealous security software is a frequent culprit. You must ensure Lumion.exe and its installation folders are whitelisted.

To avoid encountering the "Lumion 10: Your License Key is Invalid" error in the future:

Once registered, restart Lumion to re-authenticate. 2. Check for Connection Blocks

Overzealous security software blocks Lumion’s validation process. This is a leading cause of the "invalid key" error for paid users.