Is Rest API enabled for your account? As a test, can you try to create a meeting with a tool like Postman? This will help isolate the issue. In the meantime, you can also take a look at this post with a similar issue :
How I can check is REST enabled in my account ? Previously (10-15 days earlier) it was working perfectly and meeting too was created with the data but now it is not working. Should I share some more details of my account that you can look into this matter?
Upon checking on App Marketplace. It is showing that my JWT ap is deprecated. Is this is the possible reason for the same error? and if it is then should I have to create new JWT app?