I have been trying to connect to SharePoint Online, and I can do that successfully through Postman, or other Jquery services.
I Followed the instructions for oauth using this reference:
It requires an access token, which persists for 12 hours. After that, you can use a refresh token to generate a new access token. To generate the access token requires use of a web browser, not just the response from the API call. However, once the refresh token and access token are made the initial time, it will be in the response, so a web browser is not needed.
I am able to make GET calls using this method, but have not been successful with POST's, however, that is not the issue at hand. See GetITem.png for configuration in Postman and response.png as the response to that call. There is no authorization set in Postman because it uses the access token.
Directly copying this configuration over to Boomi results in a Code 400: Bad Request
I do not have to be logged in to Postman, so I do not understand why this fails. The request is definitely valid.