user6942: I've created a transaction on the TESTNET and am trying to push it via BlockCyphers facility at:
https://live.blockcypher.com/btc-testnet/pushtx/
when I make the attempt, I get the following error:

Error validating transaction: Error running script for input 0
  referencing
  261190892daa2c9aaaf25c20624f7f2941d2ad58dec883b0c929d1fa9306fd57 at 0:
  Script was NOT verified successfully..

here's the transaction.  I don't see what the matter with it is and not sure I understand the error.  can anyone help?
{
    "addresses": [
        "mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj", 
        "2N7nSZjfqikj4oVkCqaLB3CNMY3TA72PbNY", 
        "msp7depXvcjLqykZxYVrWNG9QgKqLWWKEN"
    ], 
    "block_height": -1, 
    "block_index": -1, 
    "confirmations": 0, 
    "double_spend": false, 
    "fees": 12375, 
    "hash": "463372d7a8f456c882179635aabbeca4146396b1f81c05699a2e885e3f84d6e6", 
    "inputs": [
        {
            "addresses": [
                "mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj"
            ], 
            "age": 1657999, 
            "output_index": 0, 
            "output_value": 5000000, 
            "prev_hash": "261190892daa2c9aaaf25c20624f7f2941d2ad58dec883b0c929d1fa9306fd57", 
            "script": "48304502210093b8ff9180a8a31a5ee7b0fb6c560aef888a3d53576e530cb4601dce2d3c51da02204fd8a28743f1d1100a2f56428e743501091e833550df6cf540bad4f5248a6d3c012102d794c7e1a8068782ef6ee68acf9f6ad9c84c78349671c1a7bf60418a8e1ed108", 
            "script_type": "pay-to-pubkey-hash", 
            "sequence": 4294967295
        }
    ], 
    "outputs": [
        {
            "addresses": [
                "2N7nSZjfqikj4oVkCqaLB3CNMY3TA72PbNY"
            ], 
            "script": "a9149f792783320ffb5a4f3ee4c69525d4932ac0497087", 
            "script_type": "pay-to-script-hash", 
            "value": 500
        }, 
        {
            "addresses": [
                "msp7depXvcjLqykZxYVrWNG9QgKqLWWKEN"
            ], 
            "script": "76a91486e0602ab38efd1811ff4db76f7d58c717c8598888ac", 
            "script_type": "pay-to-pubkey-hash", 
            "value": 4987125
        }
    ], 
    "preference": "high", 
    "received": "2020-01-10T05:09:49.945289619Z", 
    "relayed_by": "54.197.194.161", 
    "size": 224, 
    "total": 4987625, 
    "ver": 2, 
    "vin_sz": 1, 
    "vout_sz": 2
}

- Addendum I -
to help narrow down the solution, here's the code I'm using to produce the transaction:
I first produce an address where to receive some coin:
const btc = require('bitcoinjs-lib');
const bip39 = require('bip39');
const bip32 = require('bip32');

var mnem = 'my-12-word-bip39-seed-phrase'
var root = = bip32.fromSeed(
  bip39.mnemonicToSeedSync(mnem), bitcoin.networks.testnet
);
var p = "m/44'/1'/0'/0/0"
var pubkey = root.derivePath(p).publicKey;
var {address} = btc.payments.p2pkh({pubkey, network: btc.networks.testnet});
console.log(address);

which yields mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj.  I then send some coin to that address and attempt to create my transaction:
const CS = require('coinselect');
var feeRate = 55;
var env = 'test3'
var src = 'mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj'
var url = `https://api.blockcypher.com/v1/btc/${env}/addrs/${src}?unspendOnly=true`;
var o = await fetch(url).then(res => res.json());
var utxos = o.txrefs.map(o => ({
    txId: o.tx_hash, 
    vout: parseInt(o.tx_output_n), 
    value: parseInt(o.value)
}));
var targets = [{address: '2N7nSZjfqikj4oVkCqaLB3CNMY3TA72PbNY', value: 500}];
var {inputs, outputs, fee} = CS(utxos, targets, feeRate);
if (ret.outputs) ret.outputs.forEach(o => {
    if (!o.address) o.address = 'msp7depXvcjLqykZxYVrWNG9QgKqLWWKEN';
})

// builds the transaction
var tx = new btc.TransactionBuilder(btc.networks.testnet);
inputs.forEach(o => tx.addInput(o.txId, o.vout));
outputs.forEach(o => tx.addOutput(o.address, o.value));
tx.sign(0, root);
console.log(tx.build().toHex());

from which I get a numerical string that converts to the above transaction.  as can be seen, I'm using the same root to sign the transaction that was used to create the source address

user87716: You have the wrong public key inside your SignatureScript:  
Sig: 48-304502210093b8ff9180a8a31a5ee7b0fb6c560aef888a3d53576e530cb4601dce2d3c51da02204fd8a28743f1d1100a2f56428e743501091e833550df6cf540bad4f5248a6d3c-01
pubkey: 21-02d794c7e1a8068782ef6ee68acf9f6ad9c84c78349671c1a7bf60418a8e1ed108

The outpoint you are spending (2611[...]fd57:0) has the following PubkeyScript: 
76-a9-14-2937902660c169b9381a5b3eb35cc889a4686a85-88-ac

When the script runs it fails on 0x88 (or OP_EqualVerify) because HASH160 of the given public key (02d7[...]d108) is e652ed9163ac72629584ec92f47602cca45aa969

6942: <p>I've created a transaction on the TESTNET and am trying to push it via BlockCyphers facility at:</p>

<p><a href="https://live.blockcypher.com/btc-testnet/pushtx/" rel="nofollow noreferrer">https://live.blockcypher.com/btc-testnet/pushtx/</a></p>

<p>when I make the attempt, I get the following error:</p>

<blockquote>
  <p>Error validating transaction: Error running script for input 0
  referencing
  261190892daa2c9aaaf25c20624f7f2941d2ad58dec883b0c929d1fa9306fd57 at 0:
  Script was NOT verified successfully..</p>
</blockquote>

<p>here's the transaction.  I don't see what the matter with it is and not sure I understand the error.  can anyone help?</p>

<pre><code>{
    "addresses": [
        "mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj", 
        "2N7nSZjfqikj4oVkCqaLB3CNMY3TA72PbNY", 
        "msp7depXvcjLqykZxYVrWNG9QgKqLWWKEN"
    ], 
    "block_height": -1, 
    "block_index": -1, 
    "confirmations": 0, 
    "double_spend": false, 
    "fees": 12375, 
    "hash": "463372d7a8f456c882179635aabbeca4146396b1f81c05699a2e885e3f84d6e6", 
    "inputs": [
        {
            "addresses": [
                "mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj"
            ], 
            "age": 1657999, 
            "output_index": 0, 
            "output_value": 5000000, 
            "prev_hash": "261190892daa2c9aaaf25c20624f7f2941d2ad58dec883b0c929d1fa9306fd57", 
            "script": "48304502210093b8ff9180a8a31a5ee7b0fb6c560aef888a3d53576e530cb4601dce2d3c51da02204fd8a28743f1d1100a2f56428e743501091e833550df6cf540bad4f5248a6d3c012102d794c7e1a8068782ef6ee68acf9f6ad9c84c78349671c1a7bf60418a8e1ed108", 
            "script_type": "pay-to-pubkey-hash", 
            "sequence": 4294967295
        }
    ], 
    "outputs": [
        {
            "addresses": [
                "2N7nSZjfqikj4oVkCqaLB3CNMY3TA72PbNY"
            ], 
            "script": "a9149f792783320ffb5a4f3ee4c69525d4932ac0497087", 
            "script_type": "pay-to-script-hash", 
            "value": 500
        }, 
        {
            "addresses": [
                "msp7depXvcjLqykZxYVrWNG9QgKqLWWKEN"
            ], 
            "script": "76a91486e0602ab38efd1811ff4db76f7d58c717c8598888ac", 
            "script_type": "pay-to-pubkey-hash", 
            "value": 4987125
        }
    ], 
    "preference": "high", 
    "received": "2020-01-10T05:09:49.945289619Z", 
    "relayed_by": "54.197.194.161", 
    "size": 224, 
    "total": 4987625, 
    "ver": 2, 
    "vin_sz": 1, 
    "vout_sz": 2
}
</code></pre>

<p><strong>- Addendum I -</strong></p>

<p>to help narrow down the solution, here's the code I'm using to produce the transaction:
I first produce an address where to receive some coin:</p>



<pre><code>const btc = require('bitcoinjs-lib');
const bip39 = require('bip39');
const bip32 = require('bip32');

var mnem = 'my-12-word-bip39-seed-phrase'
var root = = bip32.fromSeed(
  bip39.mnemonicToSeedSync(mnem), bitcoin.networks.testnet
);
var p = "m/44'/1'/0'/0/0"
var pubkey = root.derivePath(p).publicKey;
var {address} = btc.payments.p2pkh({pubkey, network: btc.networks.testnet});
console.log(address);
</code></pre>

<p>which yields <code>mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj</code>.  I then send some coin to that address and attempt to create my transaction:</p>



<pre><code>const CS = require('coinselect');
var feeRate = 55;
var env = 'test3'
var src = 'mjGtZWXgPdbLUZYWtDqVTfbFieVzXFfSEj'
var url = `https://api.blockcypher.com/v1/btc/${env}/addrs/${src}?unspendOnly=true`;
var o = await fetch(url).then(res =&gt; res.json());
var utxos = o.txrefs.map(o =&gt; ({
    txId: o.tx_hash, 
    vout: parseInt(o.tx_output_n), 
    value: parseInt(o.value)
}));
var targets = [{address: '2N7nSZjfqikj4oVkCqaLB3CNMY3TA72PbNY', value: 500}];
var {inputs, outputs, fee} = CS(utxos, targets, feeRate);
if (ret.outputs) ret.outputs.forEach(o =&gt; {
    if (!o.address) o.address = 'msp7depXvcjLqykZxYVrWNG9QgKqLWWKEN';
})

// builds the transaction
var tx = new btc.TransactionBuilder(btc.networks.testnet);
inputs.forEach(o =&gt; tx.addInput(o.txId, o.vout));
outputs.forEach(o =&gt; tx.addOutput(o.address, o.value));
tx.sign(0, root);
console.log(tx.build().toHex());
</code></pre>

<p>from which I get a numerical string that converts to the above transaction.  as can be seen, I'm using the same root to sign the transaction that was used to create the source address</p>
 87716: <p>You have the wrong public key inside your SignatureScript:  </p>

<pre><code>Sig: 48-304502210093b8ff9180a8a31a5ee7b0fb6c560aef888a3d53576e530cb4601dce2d3c51da02204fd8a28743f1d1100a2f56428e743501091e833550df6cf540bad4f5248a6d3c-01
pubkey: 21-02d794c7e1a8068782ef6ee68acf9f6ad9c84c78349671c1a7bf60418a8e1ed108
</code></pre>

<p>The outpoint you are spending (<code>2611[...]fd57:0</code>) has the following PubkeyScript: </p>

<pre><code>76-a9-14-2937902660c169b9381a5b3eb35cc889a4686a85-88-ac
</code></pre>

<p>When the script runs it fails on 0x88 (or OP_EqualVerify) because HASH160 of the given public key (02d7[...]d108) is <code>e652ed9163ac72629584ec92f47602cca45aa969</code></p>
