Get error "Can not sign for this input with the key" when migrating from TransactionBuilder to Psbt

Error: Can not sign for this input with the key

I got this error when tried to create a raw transaction with testnet, p2pkh address. Everything works fine if I use TransactionBuilder, except the warning message told me should use Psbt. When using signInput method, my pubkey seems not to match with utxo input.

This is my getPrivateKey function from mnemonic string, works fine with TransactionBuilder

const seed = bip39.mnemonicToSeedSync(mnemonic);
const root = bip32.fromSeed(seed, list_networks['test']);
const child = root
    .deriveHardened(44)
    .deriveHardened(coin_type['test'].index)
    .deriveHardened(0)
    .derive(0)
    .derive(index = 0);

return bitcoin.ECPair.fromPrivateKey(child.privateKey, { network: list_networks['test'] });

And this is my new createRawTransaction

// Get Private Key From Mnemonic Word Lists 
const key = getPrivateKey(mnemonic);
// Create Psbt Instance
const psbt = new bitcoin.Psbt({ network: list_networks['test'] });
// Add Unspent transaction outputs
utxos.forEach(utxo => {
// this object is from getrawtransaction bitcoin-cli
  psbt.addInput({
      hash: utox.hash,
      index: utox.index,
      nonWitnessUtxo: Buffer.from(utox.hex, 'hex'),
  })
});
// Add Output To Destination address
psbt.addOutput({
        address: destination,
        value: amount,
});
// Sign utxos Input
for (let i = 0; i < utxos.length; i++) {
     psbt.signInput(i, key); // worked with TransactionBuilder.sign 
}

What’s missing? Shoud I stay with TransactionBuilder?

[HarryMarch]

I found out what I been missing. I passed a wrong utxo input index value. Sorry for wasting your time at the weekend. But I knew you’d show up as usual to help wandering people like me.

[HarryMarch]

I did a quick check, the private key is fine with TransactionBuilder