Woocommerce Custom Payment Gateway Order Status

I am using custom Purchase Order based payment gateway method in Woocommerce and have registered my custom status status – Pending PO Verification for all orders made using this payment method. The issue is i am getting Payment Pending message on admin and customer my account-> Order page attached screenshot for the same. admin order status screenshot and customer my account->Order page screenshot . My custom order status code below:

// WooCommerce order page status add Pending PO Verification //
// 1. Register custom order status
function register_pending_po_verification_order_status() {
    register_post_status( 'wc-pending-po-verification', array(
        'label'                     => 'Pending PO Verification',
        'public'                    => true,
        'exclude_from_search'       => false,
        'show_in_admin_all_list'    => true,
        'show_in_admin_status_list' => true,
        'label_count'               => nnoop( 'Pending PO Verification (%s)', 'Pending PO Verification (%s)' )
    ));
}
add_action( 'init', 'register_pending_po_verification_order_status' );
// 2. Add to WooCommerce order status list
function add_pending_po_verification_to_order_statuses( $order_statuses ) {
    $new_order_statuses = array();
    // Insert after 'wc-pending'
    foreach ( $order_statuses as $key => $status ) {
        $new_order_statuses[ $key ] = $status;
        if ( 'wc-pending' === $key ) {
            $new_order_statuses['wc-pending-po-verification'] = 'Pending PO Verification';
        }
    }
    return $new_order_statuses;
}
add_filter( 'wc_order_statuses', 'add_pending_po_verification_to_order_statuses' );

Attached is the link https://posterika.com/op.html of my custom Purchase Order Gateway

I have tried everything to make it work but the order status isnot changing to Pending PO Verification.

Looking forward to your help.
Thanks

I have tried all the combination like renaming the order status, hooks to change the order status but it is not working. I want you to advise me where is the issue in my code. Request a solution where the order status changes to Pending PO Verification after placing the order using Purchase Order Gateway.