遇到该问题时，需要检查服务器端是否正确处理了请求和数据。观察服务器响应的错误日志，了解错误原因。同时也需要检查客户端的代码，检查是否有错误或者漏洞导致该问题。以下是一份示例代码，可以实现图片上传功能：

// Retrofit 2.0+ interface for uploading image
public interface ImageUploadService {

   @Multipart
   @POST("uploadImage")
   Call uploadImage(@Part MultipartBody.Part image);

}

// code for uploading image
void uploadImage(Uri imageUri) {
   File imageFile = new File(getRealPathFromURI(imageUri));
   RequestBody requestFile = RequestBody.create(MediaType.parse("multipart/form-data"), imageFile);

   MultipartBody.Part imagePart = MultipartBody.Part.createFormData("image", imageFile.getName(), requestFile);

   Retrofit retrofit = new Retrofit.Builder()
         .baseUrl(BASE_URL) // your base url
         .addConverterFactory(GsonConverterFactory.create())
         .build();

   // create instance for your service
   ImageUploadService service = retrofit.create(ImageUploadService.class);

   // finally, execute the request
   Call call = service.uploadImage(imagePart);
   call.enqueue(new Callback() {
       @Override
       public void onResponse(Call call, Response response) {
           // Handle success response
       }

       @Override
       public void onFailure(Call call, Throwable t) {
           // Handle error response
       }
   });
}