I work in a Ropsten testnet. I have a Python application that sends a transaction and returns the transaction's txHash. It is possible to send a maximum of 500 transactions in one request. The application uses the web3 library. I called up a request with 500 transactions, and before that request ended, I started a new one. My application received txHash but the transaction is not visible in Etherscan. The message "Sorry, we can't locate this TxnHash" appears. Can more than one request be the cause of an invisible transaction? Can this transaction be canceled? If so why? Please, help.