IllegalArgumentException: Unable to create call adapter for interface s4.f for method a.b

Question

I am currently developing an Android program using Retrofit2. The module works well, but when I register the app on the Google Play Store and run internal tests, I get an error:

Exception Process: com.project.tosspayment, PID: 14085 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.project.tosspayment/com.project.tosspayment.MainActivity}: java.lang.IllegalArgumentException: Unable to create call adapter for interface s4.f for method a.b

I'm looking for opinions from everyone on this issue.

Here is my NetworkService.kt.

package com.project.kioask.retrofit
import com.google.gson.JsonObject<br>
import com.project.kioask.model.orderModel<br>
import retrofit2.Call<br>
import retrofit2.http.Body<br>
import retrofit2.http.Header<br>
import retrofit2.http.Headers<br>
import retrofit2.http.POST<br>


 interface NetworkService {

    @POST("/order/additem")
    fun doPostList(@Header("Authorization") token: String?, @Body dto: orderModel?): Call<orderModel>
    
    @Headers("Content-Type:application/json")
    @POST("/user/signpass")
    fun doPostToken(@Body passkey: String): Call<JsonObject>
}

Here is my MainActivity.kt.

package com.project.tosspayment<br>
import android.Manifest<br>
import android.content.Intent<br>
import android.content.SharedPreferences<br>
import android.content.pm.PackageManager<br>
import android.os.Bundle<br>
import android.util.Log<br>
import android.view.LayoutInflater<br>
import android.view.View<br>
import android.widget.Toast<br>
import androidx.appcompat.app.AlertDialog<br>
import androidx.appcompat.app.AppCompatActivity<br>
import androidx.core.app.ActivityCompat<br>
import androidx.core.content.ContextCompat<br>
import com.google.gson.JsonObject<br>
import com.google.zxing.integration.android.IntentIntegrator<br>
import com.google.zxing.integration.android.IntentResult<br>
import com.project.kioask.retrofit.NetworkService<br>
import com.project.tosspayment.databinding.ActivityMainBinding<br>
import com.project.tosspayment.databinding.CustomDialogBinding<br>
import retrofit2.Call<br>
import retrofit2.Callback<br>
import retrofit2.Response<br>
import retrofit2.Retrofit<br>
import retrofit2.converter.gson.GsonConverterFactory<br>
import java.util.regex.Pattern<br>

class MainActivity : AppCompatActivity() {

    lateinit var binding: ActivityMainBinding
    lateinit var customDialogBinding: CustomDialogBinding
    private var backPressTime:Long = 0
    
    private val REQUEST_CAMERA_PERMISSION = 1
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
    
        customDialogBinding =
            CustomDialogBinding.inflate(LayoutInflater.from(this@MainActivity))
    
        if(ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.CAMERA),REQUEST_CAMERA_PERMISSION)
        } else {
            openScanner()
        }
    
    
        val passkey = getString(R.string.backend_secretKey)
    
        val tokenRetrofit = Retrofit.Builder()
            .baseUrl("https://api.format.kro.kr")
            .addConverterFactory(GsonConverterFactory.create())
            .build();
    
        val jsonObject = JsonObject()
        jsonObject.addProperty("passkey",passkey)
    
        val tokenService = tokenRetrofit.create(NetworkService::class.java)
        val tokenCall: Call<JsonObject> = tokenService.doPostToken(passkey)
        try {
            tokenCall.enqueue(object : Callback<JsonObject> {
                override fun onResponse(call: Call<JsonObject>, response: Response<JsonObject>) {
                    if(response.isSuccessful){
                        val token = response.body()?.get("token")?.asString
    
                        val tokenSaved = getSharedPreferences("token", MODE_PRIVATE)
                        val tokenEdit: SharedPreferences.Editor = tokenSaved.edit()
                        tokenEdit.putString("token",token)
                        tokenEdit.apply()
    
                        Log.w("zio","token: $token")
    
                    }else{
                        Log.w("zio","인증실패 : ${response.code()}")
                    }
                }
    
                override fun onFailure(call: Call<JsonObject>, t: Throwable) {
                    Log.w("zio","접속실패 : ${t.message}")
                }
            })
        }catch (e: Exception){
            e.printStackTrace()
            Log.w("zio","error : ${e.message}")
        }
    }
    
    private fun openScanner(){
        val QrScan = IntentIntegrator(this)
        QrScan.setCameraId(0) //후방카메라 사용
        QrScan.setBeepEnabled(false) //스캔할때 소리 끄기
        QrScan.addExtra("PROMPT_MESSAGE","QR코드를 스캔해주세요")
        QrScan.setOrientationLocked(false)
        QrScan.initiateScan()
    }
    
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    
    
        val result: IntentResult =
            IntentIntegrator.parseActivityResult(requestCode, resultCode, data)
        val scannerData = result.contents
    
        if (scannerData == null) {
            dialog("QR코드 확인","QR코드를 다시 스캔해 주세요",
                customDialogBinding.dialogButton.setOnClickListener {
                    intent = Intent(this, MainActivity::class.java)
                    startActivity(intent)
                })
            return
        }
    
        if (requestCode == IntentIntegrator.REQUEST_CODE && resultCode == RESULT_OK) {
            val pattern =
                Pattern.compile("\\{\"orderId\":\"([A-Za-z0-9]+)\",\"price\":(\\d+),\"orderName\":\"([^\"]+)\",\"customerKey\":\"([A-Za-z0-9]+)\"\\}")
    
            val matcher = pattern.matcher(scannerData ?: "")
    
            if (matcher.find()) {
                val orderid = matcher.group(1)
                val price = matcher.group(2)?.toInt()
                val ordername = matcher.group(3)
                val customerKey = matcher.group(4)
    
                    intent = Intent(this, PayActivity::class.java)
                    intent.putExtra("orderId", orderid)
                    intent.putExtra("price", price)
                    intent.putExtra("orderName", ordername)
                    intent.putExtra("customerKey", customerKey)
    
                    startActivity(intent)
            }
            super.onActivityResult(requestCode, resultCode, data)
        }else{
            dialog("QR코드 확인","잘못된 QR코드 입니다.",
            customDialogBinding.dialogButton.setOnClickListener {
                intent = Intent(this, MainActivity::class.java)
                startActivity(intent)
            })
        }
    }
    
    override fun onBackPressed() {
        if(System.currentTimeMillis() - backPressTime < 2_000){
            finish()
        }else{
            Toast.makeText(this,"한번 더 누르면 앱이 종료됩니다.",Toast.LENGTH_SHORT).show()
            backPressTime = System.currentTimeMillis()
        }
    }
    
    fun dialog(title:String,message:String, OnClickListener: Unit) {
    
        val alertDialog = AlertDialog.Builder(this)
            .setView(customDialogBinding.customDialog)
            .create()
    
        customDialogBinding.dialogTitle.text = title
        customDialogBinding.dialogMessage.text = message
        customDialogBinding.dialogButton.text = "확인"
        customDialogBinding.dialogMessage.visibility = View.VISIBLE
        customDialogBinding.dialogButton.visibility = View.VISIBLE
    
        alertDialog.show()
    }

}