I cant get te OAuth-token from the user consent code in production. In the sandbox the whole process works without problems.
The response to my token-from-code request I get is always just a http code 400 with empty body and without any special headers that might give a clue.
I can't find any problems in my request (this is a repost without details, my original post hat all the details except the secret stuff but went to moderation, probably because of that).
Maybe I need to do the compaible app check first? The docs say I do but they also say I don't. I want to transition from the XML Trading API we are using since 15+ years step by step, starting with the finance api.