Hey,
this API key should work regardless - it is an artifact of the migration of our user management, see this post: Upcoming Migration to HeiGIT User Management (2025-02-25 10:00 CET)
It is not a JWT token - have a look at our API docs on how to use the key:
If you still have issues with your key, get in touch at support [at] smartmobility.heigit.org
Please include the request you issued and how you did so in your message.
Best regards