how to android retrofit2 500 error clear?

Question

As the postman communicates normally, there seems to be no problem on the server side.

postman

and my Retrofit2 

open class RetrofitAPI {

    private val serverIp = "http://glowprdown-env.elasticbeanstalk.com/"

    companion object {
        private val ourInstance = RetrofitAPI()
        fun getInstance() = ourInstance
    }

    private val retrofit: Retrofit = Retrofit.Builder()
        .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
        .addConverterFactory(GsonConverterFactory.create())
        .baseUrl(serverIp)
        .build()

    val sampleApi: SampleAPI = retrofit.create(SampleAPI::class.java)
    val userApi: UserAPI = retrofit.create(UserAPI::class.java)
}

for interface ( controller )

interface UserAPI {

    @POST("user")
    fun login(
        @Query("userId") userId: String?,
        @Query("userName") userName: String?,
        @Query("password") password: String?,
        @Query("phone") phone: String?,
        @Query("gender") gender: String?,
        @Query("age") age: Int?,
        @Query("email") email: String?,
        @Query("provider") provider: String?,
        @Query("pushNotiFl") pushNotiFl: String?,
        @Query("kakaoNotiFl") kakaoNotiFl: String?,
        @Query("deviceToken") deviceToken: String?,
    ) : Single<UserResponse>

}

I googled it, but I thought it was an error that could come out because the address or endpoint was different. but it wasn't

Could you possibly point out what I did wrong? plz

Answer 1

From Pif and Daniel Nugent anwser.

data class LoginRequest (
@SerializedName("userId") val userId: String?,
@SerializedName("userName")val userName: String?,
@SerializedName("password") val password: String?,
@SerializedName("phone") val phone: String?,
@SerializedName("gender") val gender: String?,
@SerializedName("age")val age: Int?,
@SerializedName("email") val email: String?,
@SerializedName("provider") val provider: String?,
@SerializedName("pushNotiFl") val pushNotiFl: String?,
@SerializedName("kakaoNotiFl")val kakaoNotiFl: String?,
@SerializedName("deviceToken") val deviceToken: String?)


interface UserAPI {
@POST("user")
fun login(
    @Body loginRequest :LoginRequest
) : Single<UserResponse>

}