401 Unauthorized response when GET-ing groups in Postman

Hi,

I am struggling to be able to do the first call to the API, ie GET /groups - I keep getting a 401 error, even though I believe I followed the steps properly (I have set api-key and api-secret as environment variables in Postman).

here's the Postman log (I've replaced the values for keyId and signature):

Proxy:
host:"10.200.72.2"
port:8080
match:"http+https://*:*/*"

Request Headers:
Date:"Tue, 03 Dec 2019 22:25:54 GMT"
Authorization:"Signature keyId="myKey-myKey-myKey-myKey-myKey",algorithm="hmac-sha256",headers="(request-target) host date",signature="mySignature-mySignature-mySignature"
User-Agent:"PostmanRuntime/7.15.2"
Accept:"*/*"
Cache-Control:"no-cache"
Postman-Token:"e47060b0-56bf-4132-b8d8-94d1b1f420e5"
Host:"rms-world-check-one-api-pilot.thomsonreuters.com"
Accept-Encoding:"gzip, deflate"
Connection:"keep-alive"

Response Headers:
Authorization:"WWW-Authenticate: Signature realm="World-Check One API",algorithm="hmac-sha256",headers="(request-target) host date content-type content-length""
Transfer-Encoding:"chunked"
Date:"Tue, 03 Dec 2019 22:25:55 GMT"
Server:""""
Connection:"close"

I saw this similar question https://community.developers.refinitiv.com/questions/48017/401-unauthorized-response-when-calling-httpget-v1g.html in which user says the issue was the endpoint, but without precising what was wrong - I am using the query from the provided Postman collection, so I guess it's

correct.

Can you help me out figure out what's wrong with my query?

Thanks