bitcoinjs – Transaction transfer failed (script not found for input #0)

I tried making a simple BTC transfer but got the following error: Script not found for input #0. What am I missing?

const bitcoin = require("bitcoinjs-lib");
const ECPairFactory = require("ecpair");
const ecc = require("tiny-secp256k1");
const  RegtestUtils  = require("regtest-client");

module.exports = async function (req, res) 
    const regtestUtils = new RegtestUtils(
        APIURL: "https://regtest.bitbank.cc/1",
        APIPASS: "satoshi",
    );

    const network = regtestUtils.network; // regtest network params

    const ECPair = ECPairFactory.ECPairFactory(ecc);
    const keyPair = ECPair.fromWIF(
        "xxxxxxxx"
    );

    const p2pkh = bitcoin.payments.p2pkh(
        pubkey: keyPair.publicKey,
        network,
    );

    const unspent = await regtestUtils.faucet(p2pkh.address, 2e4);

    const txb = new bitcoin.Psbt( network );
    txb.setVersion(2)
        .setLocktime(0)
        .addInput(
            hash: unspent.txId,
            index: unspent.vout,
        )
        .addOutput(
            address: regtestUtils.RANDOM_ADDRESS,
            value: 1e4,
        )
        .signAllInputs(keyPair);

    const tx = txb.build();

    console.log("hash", tx.toHex());

    return;

    // build and broadcast to the Bitcoin Local RegTest server
    await regtestUtils.broadcast(tx.toHex());

    // This verifies that the vout output of txId transaction is actually for value
    // in satoshis and is locked for the address given.
    // The utxo can be unconfirmed. We are just verifying it was at least placed in
    // the mempool.
    await regtestUtils.verify(
        txId: tx.getId(),
        address: regtestUtils.RANDOM_ADDRESS,
        vout: 0,
        value: 1e4,
    );

    res.status(400).json(
        error: false,
        message: address,
    );
;