Jlevers selling partner inbound shipment getShipments() api getting error Request is invalid - NextToken must not be empty"

When I am calling selling partner Amazon fba inbound shipment getShipments() api i am getting a NextToken.

But when again calling the API with NextToken it gives me below error even though NextToken exist -

[400] 
{ "errors": [ { "code": "InvalidInput", "message": "Request is invalid - NextToken must not be empty", "details": "" } ] }

Below is my code:

<?php 
    require_once(__DIR__ . '/vendor/autoload.php');

    // See README for more information on the Configuration object's options
    $config = new SellingPartnerApi\Configuration([
        "lwaClientId" => "<LWA client ID>",
        "lwaClientSecret" => "<LWA client secret>",
        "lwaRefreshToken" => "<LWA refresh token>",
        "awsAccessKeyId" => "<AWS access key ID>",
        "awsSecretAccessKey" => "<AWS secret access key>",
        "endpoint" => SellingPartnerApi\Endpoint::NA  // or another endpoint from lib/Endpoints.php
    ]);

    $api = new SellingPartnerApi\Api\FbaInboundV0Api($config);

    // Input data
    $mpId      = $_POST['txtMarketplaceId']; // Blocked since not required
    $shpStatus = $_POST['txtShpStatus'];
    
    try {
        $shipments = $api->getShipments('SHIPMENT', [$mpId], [$shpStatus]); 

        if(!empty($shipments['payload']['shipment_data'])) { 
            // Check if it has next token
            if(isset($shipments['payload']['next_token'])){
                // Get next token
                $nextToken = $shipments['payload']['next_token'];
                
                // HERE I AM GETTING ERROR 
                $resNextToken = $api->getShipments('NEXT_TOKEN', ['NextToken' => $resNextToken]); 

                print_r($resNextToken); die;
            }
        
        } else {
            echo "No shipments found"; 
        }
    } catch (Exception $e) {
        echo "Exception when calling get shipments API '.$e->getMessage()"; 
    }

?>

Am I making getShipments() request with NextToken incorrectly?

I solved this using

$api->getShipments('NEXT_TOKEN', [$mpId], null, null, null, null, $nextToken); 

Look the order of params in getShipments() method in API code

   /**
     * Operation getShipments
     *
     * @param  string $query_type Indicates whether shipments are returned using shipment information (by providing the ShipmentStatusList or ShipmentIdList parameters), using a date range (by providing the LastUpdatedAfter and LastUpdatedBefore parameters), or by using NextToken to continue returning items specified in a previous request. (required)
     * @param  string $marketplace_id A marketplace identifier. Specifies the marketplace where the product would be stored. (required)
     * @param  string[] $shipment_status_list A list of ShipmentStatus values. Used to select shipments with a current status that matches the status values that you specify. (optional)
     * @param  string[] $shipment_id_list A list of shipment IDs used to select the shipments that you want. If both ShipmentStatusList and ShipmentIdList are specified, only shipments that match both parameters are returned. (optional)
     * @param  string $last_updated_after A date used for selecting inbound shipments that were last updated after (or at) a specified time. The selection includes updates made by Amazon and by the seller. (optional)
     * @param  string $last_updated_before A date used for selecting inbound shipments that were last updated before (or at) a specified time. The selection includes updates made by Amazon and by the seller. (optional)
     * @param  string $next_token A string token returned in the response to your previous request. (optional)
     *
     * @throws \SellingPartnerApi\ApiException on non-2xx response
     * @throws \InvalidArgumentException
     * @return \SellingPartnerApi\Model\FbaInboundV0\GetShipmentsResponse
     */
    public function getShipments($query_type, $marketplace_id, $shipment_status_list = null, $shipment_id_list = null, $last_updated_after = null, $last_updated_before = null, $next_token = null)
    {
        $response = $this->getShipmentsWithHttpInfo($query_type, $marketplace_id, $shipment_status_list, $shipment_id_list, $last_updated_after, $last_updated_before, $next_token);
        return $response;
    }