The Partners API uses standard HTTP response codes to show if an API request was successful or unsuccessful. All in all: Success is indicated by codes in the range 2xx. Codes in the 4xx range signify errors that couldn't be fixed based on the information available (e.g., a necessary parameter was left out, etc.). A server error (rare) is indicated by codes in the 5xx range.
Have a look at the error below you are encountering to go straight to the causes as well as solutions
| 200 | OK |
| 201 | Created |
| 400 | Bad Request |
| 401 | Invalid Key |