After the recent changes to the KNM API calls when trying to access the API as per the below help link, we are getting the below error.
To overcome this issue it is recommended that you use the API key.
Create an API key for your username by going to Network Monitor=>User=>My Settings->Basic properties and click new if there is no entry or copy the entry that already exists in the API Key: field.
Once you get the API key there would be a change in the URL's which would allow you to access the KNM API.
Note: The API key generated is user-specific.