Hey @micu,
Thanks for reaching out about this, and happy to help.
Are you using the C# library from jwt.io, or a different library? Can you let me know if this thread helps:
C# JWT token invalid - #6 by tommy
If the JWT token generated via the Zoom marketplace is working for you, this is most likely an issue with the code you’re using to generate the token programmatically.
Let me know if either of the resources linked in the attached thread help, though!
Best,
Will