the self-service app https://addon.mendix.com currently has the requirement that a Mendix app that you want to onboard in AQM was deployed at least once on any mendix cloud including sandbox.
We are working on changing that addon.mendix.zom in such a way that it will no longer check the deploy api if the provided credentials are correct.
I hope your app was onboarded in AQM by now? otherwise just send us a support email email@example.com and then we will look at your request
best regards Michiel Cuijpers