Solution comment by Adobe: "Such kind of issues comes when integration
is not done correctly. So the reason why the API integration is not
working for you might be using the integration created for Stage
instance for firing API calls on Prod. If there is single integration
point created which is linked to Stage instance and if someone will use
it for firing calls to Production instance it will not work. You have to
create two separate integrations for stage and prod and accordingly use
the same....