Error when trying to deploy an Application via App Engine Studio

Hi All,

I'm having an issue when trying to deploy a Scoped Application via App Engine Studio (Pipelines and Deployments).

We activated the AES plugins and configured environments as well as the pipeline.

Validation of the non-prod as well as the controller environment is successful, however when I try to submit an App via "Submit" in AES, a "Bad Request" error message is displayed. 

In Flow Designer executions I can see that the "Pipeline Runner" Action that has been called received a "Failed to verify request from source instance id ..." when calling the Pipeline API on the controller instance.

Has anyone had similiar issues or could provide guidance on how to fix this?

Thanks

Jannik