
Answer to my self, you probably also need to register a new app specific for sandbox.geni.com, as a you have to register as a new user there: https://sandbox.geni.com/platform/developer/apps
I have updated the project with info about the sandbox: https://www.geni.com/projects/The-Geni-API/1124
Private User - Can you delete my user and data at https://sandbox.geni.com so I can restart without using another email? I set a permanent password which I can't remember or does not work and https://sandbox.geni.com/login/reset_password does not end up in my mailbox (says it is sent to b**x@e*******o)
Felipe Grice - From my update of this project description:
If you plan making an app which will upload or modify data in Geni it is strongly advised to start in the sandbox which is a parallell server where you don't risk destroying or making false data in the world tree