Error: Invalid Credentials, Error: invalid_client

Possible cause:

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

• The clientid is not present in the connect/token call.
• The clientid is incorrect during the connect/token call.
• The clientid is mismatched between the connect/authorization, connect/token calls.
• The clientid is used when creating the client_assertion / client_secret is incorrect/mismatched or not present.
• Invalid/wrong client_assertion / client_secret used in the connect/token call can also return “Error: invalid_client”.

See screenshot below : 

Steps To Resolve:

• Ensure client_id  is present in the connect/token call.
• Ensure the client_id used when creating client_assertion and making connect/token calls is a valid client ID.
• Ensure client_assertion value is valid, and there are no white spaces.