Facebook payment, API Error Code: 1383008

I am getting API Error Code: 1383008 ,when i try to open Facebook pay dialog in canvas app, I checked my callback URL is working in testing, What should i do to fix it?

Error screenshot

The problem is that in your callback you just copied the sample for RTU implementation instead of the payments callback implementation; You need to return the price for the item that you're trying to sell. There are two solutions to this: either set the price in the OG object by adding this meta tags

<meta property="product:price:amount" content="0.10"/> 
<meta property="product:price:currency" content="USD"/> 

or responding to the callback correctly:

<?php

try {
  if (isset($_POST) && isset($_POST['method'] && $_POST['method'] == "payments_get_item_price")) {


    $response = new StdClass();
    $response->content = new StdClass();
    $response->content->product = 'onetentechnology.com/devovertesting/coin.html';
    $response->content->amount = 1.0; //price
    $response->content->currency = $_POST['user_currency']; 
    $response->method = "payments_get_item_price"; 

    echo(json_encode($response));
  }
}
catch($error){
}
?>