Verify that the URLs (for OAuth2.0 authentication and the actual service endpoint) you are attempting to use are the TEST URLs (NOT the SANDBOX  URLs that might have been used in prior requests).

Ensure your application is using the Client ID and Client Secret specific to the TEST environment. These credentials are retrievable in your application Dashboard.

After you have made these updates to your collection, you can now test various scenarios by changing the test PII in the request to known test cases.

Look in the Additional API Docs tab on the Product page for CTEST files containing various defined test cases.

NOTE: You must have an active Test Member Number set up with the product(s) you are attempting to test. If you do not yet have a test member number, please contact your Equifax account executive.