I also faced the same issue, but the trick was I implemented both the methods that were stated earlier in the stack.First I turned off the postman proxy as shown in below image.
I was not able to make any calls from postman to docker container running Couchbase Server. Very frustrating. Turns out I had proxy setting configured to some aws instance which has been long deleted.
If you have active proxy in your system then make sure Global Proxy Configuration and Use System Proxy are turned off. To do this go to Postman preferences > Proxy. You can also try sending a request in postman without typing localhost (e.g. :8080/send)
But for the past few days, I've been trying to do the same action either via postman or via lunix command line by doing a curl -X POST https:... and nothing works. As you said, maybe it's an authentication problem?
Great example on getting up and running on MLE requests quickly in postman. Especially insightful was the fact that for encryption we needed the Server Encryption Certificate instead of the client certificate if generated via CSR.
I'm not sure what the missing piece. I've double-checked my bearer authorization and I know that's accurate. I don't think I'm giving postman enough information to parse the csv file. I defined the course_id as a variable... maybe I need to add something under parameters?