Using private application I have regenerated the private and public keys, uploaded the X509 certificate to the app and regenerated the secret and consumer keys to store back in our application. The authorization has still failed and I'm unsure about the response which reads "The access token has not been authorized C or has been revoked by the user" Specifically, the capital "C" appearing in the response.
What actually is "revoked by the user"? Presuming a client might have done something (no-one putting their hand up atm).
Is there a possibility the app is the issue? What happens to data on Xero for the client if the app is deleted and a new one created? Or is the app merely a means of connecting? Any help appreciated.