NodeJS web3: getting returned transaction hash, but it can't be located on block explorer

Question

After getting the follwowing error all the time:

Insufficient funds. The account you tried to send transaction from does not have enough funds. Required 250000000000000 and got: 0.

I commented out the gacPrice from my txData as follows:

const txData = {
        nonce: web3.utils.toHex(txCount),
        gasLimit: web3.utils.toHex(40000),
        //gasPrice: web3.utils.toHex(10e9),
        to: addressTo,
        from: addressFrom,
        data: functionAbi
}

And now I am getting a tx hash returned as a result, but this tx hash can't be located via etherscan or any other blockexplorer. What else can I do to execute successfully a transaction on Kovan ? This is my smart contract:

pragma solidity ^0.4.24;

contract Test2 {
    address public bank;

    struct Box {
        uint size;
    }
    Box public box;

    constructor() public {
        box.size = 3;
        bank = 0xa2079636...;
    }

    function changeBox(uint _change) public {
        box.size = _change;
    }

    function getBox() public returns (uint) {
        return box.size;
    }  
}  

And here is how I execute it via web3.js (full code):

const Web3 = require('web3')
const Tx = require('ethereumjs-tx')

const web3 = new Web3(new Web3.providers.HttpProvider('https://kovan.infura.io/apikey'))
const addressFrom = '0x002D18...'
const privKey = '240462...'
const addressTo = '0x36075430619b21Fff798454e2D5C81E9C18DEe81'

var contractABI = new web3.eth.Contract(
    [...abi...], addressTo);

const contractFunction = contractABI.methods.changeBox(5);
const functionAbi = contractFunction.encodeABI();

function sendSigned(txData, callback) {
    //const privateKey = new Buffer(config.privKey, 'hex')
    const privateKey = Buffer.from(privKey, 'hex');
    const transaction = new Tx(txData)
    transaction.sign(privateKey)
    const serializedTx = transaction.serialize().toString('hex')
    web3.eth.sendSignedTransaction('0x' + serializedTx, callback)
}

web3.eth.getTransactionCount(addressFrom).then(txCount => {
    // construct the transaction data
    const txData = {
        nonce: web3.utils.toHex(txCount),
        gasLimit: web3.utils.toHex(40000),
        //gasPrice: web3.utils.toHex(10e9), // 10 Gwei
        to: addressTo,
        from: addressFrom,
        data: functionAbi
        //value: web3.utils.toHex(web3.utils.toWei(123, 'wei'))
  }

    sendSigned(txData, function(err, result) {
        if (err) return console.log('error', err)
        console.log('sent', result)
    })

})

Answer 1

Receiving transaction address from the web3 may not always conclude to a successful transaction.Web3 returns transaction hash for all submitted transactions. Check the callback to identify the status of the transaction and actual block address(if succeeded).