alright my bad, thank you so much for guiding me towards a solution, via the payload I could see that there was an error in the API KEY used, which was not set correctly for production (but only for development).
Not sure why the error triggered was something that seemed unrelated but the payload included the correct message, so that the application was not found (due to the wrong key).
All up and running now also in production, thank you again for your time and help