I have an id of created article and I also can get the status of the article by GET method:
{article_id}?access_token={access_token}
I get a response like:
{
  "id": {article_id},
  "status": "SUCCESS"
}
But when I try to delete the article by the DELETE method with the same params I'm getting this response:
{
  "error": {
    "message": "(#240) Requires a valid user to be specified (either via the session or via the API parameter for specifying the user.",
    "type": "OAuthException",
    "code": 240,
    "fbtrace_id": "GsXXXXBjq"
  }
}
Everything was done according to the documentation.
I'm using v2.6 graph version whit this permissions:
publish_pages, pages_manage_instant_articles, manage_pages
I use a page token that do not expire, I got it by @Simon.Ponder's answer.
I have the only one admin user for the application and the page.
How can it be solved?