I created a Google group from the Google Groups homepage and have added 5 users.
I am trying to use the Google Admin SDK API to retrieve the list of members from my group but whenever I try the API (from the API explorer) I get a 400 :
{
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "invalid",
    "message": "Invalid Input"
   }
  ],
  "code": 400,
  "message": "Invalid Input"
 }
}
The request is :
GET https://www.googleapis.com/admin/directory/v1/groups/my-group-name%40googlegroups.com/members?key={MY_API_KEY}
My groupKey is urlencoded my-group-name@googlegroups.com
I tried using only my-group-name as the groupKey but I then get a 404 "Resource Not Found: groupKey"
I am logged in with the owner of the group and have all scopes required during the OAuth2 authentication.