I accidentally executed the unregister API call on one of the five default sandbox accounts (username: sbMemXXX2, password: sbMemXXX2#123) when I was playing around with Test Drive. Attempting to log into it in Test Drive will return {"error":["Invalid User Credentials"]}. My other four sandbox accounts still work properly.
According to the docs, the register3 API functionality is disabled for the sandbox endpoint so I'm not sure how I can recover or remake this sandbox account. Does anyone know how to do this or do I need to contact Yodlee support?
Yes you are right, you won't be able to register a user in developer sandbox environment. We recommend you to use the remaining 4 pre-provisioned user for testing purpose.
Hope this helps
Regards,
Krithik