Why has my request failed with "invalid_client"? Naomi May 22, 2020 09:01 Follow Because your client has failed to authenticate on our side. Solution Still having problems? Check if your client_secret is correct. You should have kept this in a safe place somewhere. You can generate a new client_secret through the TrueLayer Console, under App Settings → Reset Client Secret. This time don’t forget to save your client-secret somewhere safe and memorable. Check the URIs that you are using If you are testing your app in our isolated Sandbox environment, you will need to change the request URI from https://auth.truelayer.com/ to https://auth.truelayer-sandbox.com/. You can also download our dedicated TrueLayer Sandbox Data API Postman collection, where this has already been completed. More If you need more information... Have a look at our comprehensive list of the authentication error descriptions in our API documentation. Check out our Guide "Getting started with Data API". Related articles Why has my request failed with "invalid_grant"? Why has my request failed with "unauthorized_client"? Getting Started with Data API Why am I getting "invalid_request"? Why has my request failed with "internal_server_error"?