401 errors relate to authentication, and are usually caused by incorrect credentials in your request. Make sure you have the Manage API credentials role, or ask your Adyen administrator to check the following:
- If using web service user then make sure that its name and password are correctly formatted for basic authentication;
- If using an API key make sure that it has not been changed recently, or pasted incorrectly;
- If using local Terminal API, make sure that the Terminal API request is encrypted with the correct security key configured on the terminal
- Make sure that the web service user associated with the API key has all the necessary roles enabled;
- If possible, generate a new web service user and API key, and try using the new API key.