Android Java: Retrofit2 + google api auth with email and password gives 404

I've implemented auth with Firestore and it works fine and now redoing it via Google API and get http status "404" and empty message:

D/RESPONSE FIREBASE: Response{protocol=h2, code=404, message=, url=https://identitytoolkit.googleapis.com/v1/accounts/signInWithPassword?key=000080511101}

Network service:

public class NetworkService {
    private static NetworkService instance;
    private static final String BASE_URL
        = "https://identitytoolkit.googleapis.com/v1/";
    private Retrofit retrofit;

    private NetworkService() {
        retrofit = new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build();
    }

    public static NetworkService getInstance() {
        if (instance == null) {
            instance = new NetworkService();
        }
        return instance;
    }

    public PlaceHolderApi getJsonApi() {
        return retrofit.create(PlaceHolderApi.class);
    }
}

Api

public interface PlaceHolderApi {

@FormUrlEncoded
@POST("accounts/signInWithPassword")
Call<Transaction.Result> loginWithEmail(
    @Query("key") String key,
    @Field("email") String email,
    @Field("password") String password,
    @Field("returnSecureToken") boolean returnSecureToken
    );

}

Usage:

    NetworkService.getInstance()
        .getJsonApi().loginWithEmail("000080511101", email, password, true)
        .enqueue(new Callback<Transaction.Result>() {
            @Override
            public void onResponse(Call<Transaction.Result> call, Response<Transaction.Result> response) {
                Log.d("RESPONSE FIREBASE", response.toString());
                Log.d("RESPONSE MESSAGE", response.message());
            }

            @Override
            public void onFailure(Call<Transaction.Result> call, Throwable t) {
                t.printStackTrace();
            }
        });

Documentation says that I should use Content type application/JSON, but how to use it here or pass it via http using retrofit?
Any directions will be helpful.

Thanks!

UPD: Console query result

The real issue was because of colon symbol inside url ":", so url should start from dot and slash symbols "./":

    @POST("./accounts:signInWithPassword")

Found this on github and it helps https://github.com/square/retrofit/issues/2730

UPD: A little explanation why I used url like "accounts/signInWithPassword" with slash symbol inside instead of colon symbol: I tried with colon first, but got an error "Malformed url" so I dug a bit deeper with that mistake

You can add a header like this. But I think if you miss the header response, the error code wouldn't be 404.

Anyway, try this.

@FormUrlEncoded
@Headers({"Content-Type: application/json"})
@POST("accounts/signInWithPassword")
Call<Transaction.Result> loginWithEmail(
    @Query("key") String key,
    @Field("email") String email,
    @Field("password") String password,
    @Field("returnSecureToken") boolean returnSecureToken
);