FCM Auth2 subscribe to topic erro: Authentication using

I am trying to send a notification to a group of devices (topic) usin Auth2.
So first I tried to send a message to single device, and it worked OK.

Now I want to create the topic.
So I use this code that is attached at the bottom, but I get the result:

result= {“error”:”Authentication using server key is deprecated. Please use an OAuth2 token instead.”}

The access-token is the same as I use for sending one message.

The code:

$topic="{$card_id}_{$type}_{$locale}";
$url = "https://iid.googleapis.com/iid/v1:batchAdd";
$json=["to" => "/topics/{$topic}", "registration_tokens" => [$fcm_token]];
$result=send_2_FCM($json,$url);

function send_2_FCM($data,$url)
{
  require_once('firebase_access_token.php');
  $access_token=getAccessToken();

  $headers = array(
    "Authorization: Bearer $access_token",
    "Content-Type: application/json"
  );

  $ch = curl_init();
  curl_setopt( $ch,CURLOPT_URL,$url);
  curl_setopt( $ch,CURLOPT_POST,true);
  curl_setopt( $ch,CURLOPT_HTTPHEADER,$headers);
  curl_setopt( $ch,CURLOPT_RETURNTRANSFER,true);
  curl_setopt( $ch,CURLOPT_SSL_VERIFYPEER,false);
  curl_setopt( $ch,CURLOPT_CAINFO, "cacert.pem");
  if ($data)
  {
    curl_setopt( $ch,CURLOPT_POSTFIELDS,json_encode($data));
  }
  $result = curl_exec($ch);
  $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  curl_close($ch);
  debug_log("send_2_FCM: result= $result");
  if ($result && strpos($result,'"error"')) return 0;
  return 1;
}