Why someone come back to post unhelpful info, dunno.
It's the holidays, and I use postman, and like guessing games. Bet's it's the "Authorization" wasn't set in the tab. Postman generally shows a "green dot" if stuff is set. Maybe not, but the "Authorization" tab needs to be set to "Basic Auth" and your username/password* – no "green dot" in the original for REST to work on the postman side.
*Postman does scheme to mange passwords/variables, RTFM