Unable to broadcast transactions

Hi, I am currently getting the following error back when performing a broadcast:

"code" => -32000
  "message" => "unknown key:unknown key: "
  "data" => array:4 [
    "code" => 13
    "name" => "N5boost10wrapexceptISt12out_of_rangeEE"
    "message" => "unknown key"
    "stack" => array:4 [
      0 => array:3 [
        "context" => array:6 [
          "level" => "warn"
          "file" => "transaction_util.cpp"
          "line" => 107
          "method" => "verify_authority"
          "hostname" => ""
          "timestamp" => "2023-04-28T08:14:34"
        ]
        "format" => "${what}: "
        "data" => array:2 [
          "sigs" => array:1 [
            0 => "STM7cvbEbqmAWjbKyzeVTfMsi5zutoBLwJ9PxCnLGbZQ6qZkLZHgC"
          ]
          "what" => "unknown key"
        ]
      ]

I first got it when trying to configure custom_json to work but also get it for the vote example as a means to test if my params are just wrong.

My current code for the vote example is below:

$vote = new stdClass;
$vote->voter = env('HIVE_USERNAME');
$vote->author = 'mahdiyari';
$vote->permlink = 'dhf-proposal-hive-related-development';
$vote->weight = 5000;
$op = array("vote", $vote);

$hive = new Hive();
// transaction built
$trx = $hive->createTransaction([$op]);
$privateKey = $hive->privateKeyFrom(env('HIVE_KEY'));
// transaction signed
$signed = $hive->signTransaction($trx, $privateKey);
$broadcast = $hive->broadcastTransaction($signed);        

The return public key is correct and I have tested that I am using the right key via a quick transaction on JsonDoctor. I have also tried the inline method with the same error result.

Any ideas are welcome.