You are not permitted to view the requested resource

I’m getting this error using Discourse API:

{
    "errors": [
        "You are not permitted to view the requested resource."
    ],
    "error_type": "invalid_access"
}

The URL I’m trying to access via GET is https://community.makeroid.io/directory_items.json?period=monthly&order=likes_received&api_key=X&api_username=system
Tested from Postman and cURL

However, using period=all works fine