Hello,
Sorry for replying this late, as I have just run into similar issue as not being able to call a very simple GET request from localhost.
My issue was related to insecure/ self signed certificate by localhost being rejected by postman’s default setting
As soon as I toggle off the SSL cert verification option in postman I can now make the GET request.
Although this may not be related to your issue’s cause, I hope it will help other novices developers like me in the future.
Many thanks