For anyone else who comes across this issue, you can find the option to edit cookies below the “Send” button. Removing all of them by clicking the “x” allowed me to make post requests successfully.
This should be pinned to the top of the API section. POSTMAN is a terrible API development tool - the chrome app version doesn’t even let you get rid of the cookies. Migrated my calls to PAW and it worked flawlessly without extra added cookie junk.
Was running into this issue and found that I needed to download the latest version of the Postman NATIVE app to get this to work. Triple check you’re using the native app, because I thought I was and it was actually a desktop launcher for a chrome extension.
Removing the cookies from Postman fixed my strange issue of getting the Shopify login screen returned in HTML instead of the JSON response when creating a new customer. Thanks for the tip Jason! Not sure what causes those cookies, but at least i have a fix.