Try to start from a new API and Call and set headers directly in API Call in lowercase
If this doesn’t work, try to send the request to a requestbin.com and do the same in postman and compare both calls.
I now have the same issue trying to connect to a POST API to Pipedrive and working fine in postman and with the GET call but keeps giving me error 400 I have tried putting Data: before the JSON but that doesn’t work did anyone have anyone find a way to resolve this? The Pipedrive plugin from rapid dav is very limited so needs to be api