I'm making a request to the following API
curl -i -X POST "https://graph.facebook.com/PAGE-ID/messages ?recipient: { comment_id: COMMENT-ID } &message: { "text": "Thanks for reaching out, how can I help?" } &access_token=PAGE-ACCESS-TOKEN"
But I'm getting the error that is being seen on the screenshot. How to fix it?
Your screenshot doesn't show you actually do provide an access token.
Postman allows meta tokens to be sent privately via Authorization, that must not be the problem
Implement the call as you would implement it later on or use the Graph API Explorer instead to make that test call.