Error: Invalid Grant Error: invalid_grant

Possible cause:

There are quite some possible reasons why you could be getting invalid_grant. See a list of likely causes below:

• The client_assertion used is expired.
• The client_assertion used is invalid.
• The client_assertion used is missing(not present) in the API call

See screenshot below : 

Steps To Resolve:

• To fix this error ensure that you're appending the client_assertion to your connect/token API call.
• Validate the JWT generated correctly using the widget in our developer documentation or JWT.io.
• Ensure that the clientid used for the authorization and token endpoint matches the clientid used to generate the client_assertion.