I tried it within my Node app and it worked, so maybe it’s related to Postman. Also, I had a typo inside my redirect_uri, but I don’t think that that was the issue. It’s fixed now, thank you. 
I tried it within my Node app and it worked, so maybe it’s related to Postman. Also, I had a typo inside my redirect_uri, but I don’t think that that was the issue. It’s fixed now, thank you.