I've setup an App in Azure using instructions from various places, including: http://www.ktskumar.com/2017/01/access-sharepoint-online-using-postman/ http://tech.bool.se/basic-rest-request-sharepoint-using-postman/
Tried other endpoints such as https://cityofstirling.sharepoint.com/_api/contextinfo but all resulted in the 403 error.
I've granted full access to collections for the App. Does anyone have any ideas that I could explore further? Thanks for your help.