Cause
The grant lacks the highlights.activate path with can_publish, needed to activate or schedule a highlight.
What to do
Send the highlight as a draft or ask the administrator to grant activation.
application/problem+json
{
"type": "https://masnet.com/developers/errors/activate_not_granted",
"title": "Activation not granted",
"status": 403,
"detail": "...",
"code": "activate_not_granted",
"correlation_id": "..."
}