/sell/inventory/v1/inventory_item API showing 2003 Internal Error

[muhatay-64]

I have created sandbox account and created location successfully. I am trying to call get inventory items API but its showing 2003 Internal error. I don't know what's wrong here. Get locations API is working fine for me but get inventory items is failing. Following is response of API:

"errors" => array:1 [
    0 => array:6 [
      "errorId" => 2003
      "domain" => "ACCESS"
      "category" => "APPLICATION"
      "message" => "Internal error"
      "longMessage" => "There was a problem with an eBay internal system or process. Contact eBay developer support for assistance"
      "parameters" => array:1 [
        0 => array:2 [
          "name" => "code"
          "value" => "415"
        ]
      ]
    ]
  ]