Transactions go into the queue if the merchant is not having enough balance in his account process. You can mark the transaction as failed using the setQueueTxnFlag API command if enough balance is not available.
The payoutMerchantId is different from PayU Merchant Id. Check the Payouts Dashboard or call the PayU Customer Support if you don’t know your payoutMerchantId.
For sample request and response, refer to Sample Request and Response for Initiation & Tracking APIs.