Order Status not Changing

I can capture (or) output what api sent to me such as transaction id, amount, etc.

but i can’t change order status Pending Payment to Processing.

Here my code.

<?php
if ( in_array( 'woocommerce/woocommerce.php', apply_filters( 'active_plugins', get_option( 'active_plugins' ) ) ) )
{
	function wingpay_callback()
	{
		if(isset($_GET['wingpay_callback']))
		{
			global $woocommerce;
			@ob_clean();			

			$gateways = $woocommerce->payment_gateways->payment_gateways();

			if (!isset($gateways['wc_paymentwing']))
			{
				error_log('Wing plugin not enabled in woocommerce');
				return;
			}
			$wing = $gateways['wc_paymentwing'];

			$data = file_get_contents("php://input");
			$json=json_decode($data,true);

			if($json['tstatus'] == '200'){

				$tid = $json['tid'];
				$account = $json['account'];
				$amount = $json['amount'];
				$token = $json['token'];

				$order = new WC_Order($order_id);

				//echo $tid . '<br/>';

				$order -> add_order_note(__('Wing - Payment status is processing<br/>Transaction ID from Wing:', 'wc_paymentwing').' '.$tid);
				$order -> update_status('processing');			

			//echo "success";
			} else echo "fail";
		}
	}
	add_action('init', 'wingpay_callback');
}

Please advice for me!

https://wordpress.org/plugins/woocommerce/