Getting 403 for https://api.linkedin.com/v2/messages

Question

When I am trying to use #linkedins POST https://api.linkedin.com/v2/messages API with the following body

{
  "recipients": [
    "urn:li:person:xxxxxxx"
  ],
  "subject": "Group conversation title",
  "body": "Hello everyone! This is a message conversation to demo the Message API.",
  "messageType": "MEMBER_TO_MEMBER",
  "attachments": [
    "urn:li:digitalMediaAsset:xxxxxx"
  ]
}

I am getting

{
    "serviceErrorCode": 100,
    "message": "Not enough permissions to access: POST /messages",
    "status": 403
}

can you please guide me how can I get this permissions

I have try to fill various #linkedin forms and also I am sharing my access token details with you

Created on:
about 19 hours ago (1712061182 UTC)
Last authorized:
about 19 hours ago (1712061182 UTC)
Expires:
in about 2 months (1717245186 UTC)
Authentication type:
3-legged
Permissions:
email, openid, profile, r_1st_connections_size, r_ads, r_ads_reporting, r_basicprofile, r_organization_admin, r_organization_social, rw_ads, rw_organization_admin, w_member_social, w_organization_social
Status:
OAuth token is active