Trouble with calling "executeTransaction" function on timelock contract

The transaction was already queued but can't execute now.

To use empty string as a value of signature parameter, I used '' as a parameter when call queueTransaction, used "" when call executeTransaction as a parameter. And calling executeTransaction is failed with this error: "Timelock::executeTransaction: Transaction hasn't been queued."

Here is piece of the timelock contract code.

  function queueTransaction(address target, uint value, string memory signature, bytes memory data, uint eta) public returns (bytes32) {
    require(msg.sender == admin, "Timelock::queueTransaction: Call must come from admin.");
    require(eta >= getBlockTimestamp().add(delay), "Timelock::queueTransaction: Estimated execution block must satisfy delay.");

    bytes32 txHash = keccak256(abi.encode(target, value, signature, data, eta));
    queuedTransactions[txHash] = true;

    emit QueueTransaction(txHash, target, value, signature, data, eta);
    return txHash;
  }

  function executeTransaction(address target, uint value, string memory signature, bytes memory data, uint eta) public payable returns (bytes memory) {
    require(msg.sender == admin, "Timelock::executeTransaction: Call must come from admin.");

    bytes32 txHash = keccak256(abi.encode(target, value, signature, data, eta));
    require(queuedTransactions[txHash], "Timelock::executeTransaction: Transaction hasn't been queued.");
    require(getBlockTimestamp() >= eta, "Timelock::executeTransaction: Transaction hasn't surpassed time lock.");
    require(getBlockTimestamp() <= eta.add(GRACE_PERIOD), "Timelock::executeTransaction: Transaction is stale.");

    queuedTransactions[txHash] = false;

    bytes memory callData;

    if (bytes(signature).length == 0) {
      callData = data;
    } else {
      callData = abi.encodePacked(bytes4(keccak256(bytes(signature))), data);
    }

    // solium-disable-next-line security/no-call-value
    (bool success, bytes memory returnData) = target.call.value(value)(callData);
    require(success, "Timelock::executeTransaction: Transaction execution reverted.");

    emit ExecuteTransaction(txHash, target, value, signature, data, eta);

    return returnData;
  }