Trouble with flightaware api in kotlin

FlightAware AeroAPI
1

Here is my code:

val client = HttpClient(CIO)
try {
val apiKey = “key”

            val response: HttpResponse = client.get("https://api.flightaware.com/api/flights/search") {
                header("x-apikey", apiKey)
                parameter("query", "-latlong \"51.442 -0.520 51.491 -0.370\"")
                parameter("max_pages", 1)
            }

            val responseBody: String = response.body()

            val aircraftList = mutableListOf<String>()
            if (responseBody.isNotEmpty()) {
                try {
                    val jsonResponse = JSONObject(responseBody)
                    val flights = jsonResponse.optJSONArray("flights")

                    if (flights != null) {
                        for (i in 0 until flights.length()) {
                            val flight = flights.getJSONObject(i)
                            val ident = flight.optString("ident", "Unknown Ident")
                            val origin = flight.getJSONObject("origin").optString("name", "Unknown Origin")
                            val destination = flight.getJSONObject("destination").optString("name", "Unknown Destination")
                            val altitude = flight.getJSONObject("last_position").optInt("altitude", 0)
                            val latitude = flight.getJSONObject("last_position").optDouble("latitude", 0.0)
                            val longitude = flight.getJSONObject("last_position").optDouble("longitude", 0.0)
                            val heading = flight.getJSONObject("last_position").optInt("heading", 0)

                            aircraftList.add("Flight: $ident\nOrigin: $origin\nDestination: $destination\nAltitude: $altitude feet\nCoordinates: ($latitude, $longitude)\nHeading: $heading°\n-----")
                        }
                    } else {
                        println("No flights")
                    }
                } catch (e: Exception) {
                    println("Error: ${e.message}")
                }
            } else {
                println("Empty response body")
            }

            withContext(Dispatchers.Main) {
                val textView = findViewById<TextView>(R.id.tvText)
                textView.text = aircraftList.joinToString("\n\n")
            }
        } catch (e: Exception) {
            println("Error making request: ${e.message}")
            withContext(Dispatchers.Main) {
                val textView = findViewById<TextView>(R.id.tvText)
                textView.text = "Error fetching flight data: ${e.message}"
            }
        } finally {
            client.close()
        }

I keep getting this response: “Error fetching flight data: null”. My API key works as I have tested it on the website and Im just wondering what went wrong here. I’m trying to get the api to return all flights within a box of coordinates.
Thank you.