Why did I get the error “Incorrect API credentials” when I tried to make an API call?

Issue
PayPal notified you that your REST API credentials are incorrect.

Cause
This error is related to the REST API credentials you use to make API calls.

Solution
If you previously had your application set up for testing in the Sandbox environment, you may need to switch your current API credentials mode from Sandbox to Live (or vice versa). Here’s how:

  1. Log in to the PayPal Developer Portal.
  2. Click Dashboard.
  3. Select the app you’ll be editing under My Apps & Credentials.
  4. Toggle the app from Sandbox to Live or from Live to Sandbox.
  5. Use the Live or Sandbox API Credentials displayed to set your credentials in your API call appropriately. 
 
See also:
Why do I get the error “You do not have permission to perform this action” in the live environment?