Nested attributes is not saved (Devise Registration Controller/Rails 5) - ruby-on-rails

Question

I'm trying to add a nested attributes to my signup form (generated by devise), but it didn't work.
To give a brief explanation:
A user has many locations, and each location has a label name (home,eg.) and an address.
What I wanted to do here is to allow new user to register their location(nested attributes) in the signup form.
In other words, to create a new location, which is associated with the new user.
*I have already set up strong params and controllers, by referring to stackoverflow threads and other sources.
Here's my codes:
User Model
class User < ApplicationRecord
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :validatable
has_many :locations, dependent: :destroy
validates :first_name, presence: true
validates :last_name, presence: true
validates :email, presence: true
accepts_nested_attributes_for :locations
end
Location Model
class Location < ApplicationRecord
belongs_to :user
validates :label, presence: true
validates :address, presence: true
geocoded_by :address
after_validation :geocode, if: :will_save_change_to_address?
end
My Signup Form
<%= simple_form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %>
<div class="form-inputs">
..........
<%= f.simple_fields_for :location do |p| %>
<%= p.input :address %>
<%= p.input :label, collection: ['Home', 'Work'] %>
<% end %>
<%= f.button :submit, "Sign up", class: "btn btn-long" %>
</div>
<% end %>
Registration Controllers (Devise)
class Users::RegistrationsController < Devise::RegistrationsController
before_action :configure_sign_up_params, only: [:create]
def new
build_resource({})
self.resource.locations.build
respond_with self.resource
end
protected
def configure_sign_up_params
devise_parameter_sanitizer.permit(:sign_up, keys: [:email, :first_name, :last_name, :password, :photo, locations_attributes: [:label, :address]])
end
end
Application Controller
class ApplicationController < ActionController::Base
protect_from_forgery with: :exception
before_action :authenticate_user!
before_action :configure_permitted_parameters, if: :devise_controller?
def configure_permitted_parameters
devise_parameter_sanitizer.permit(:sign_up, keys: [:email, :first_name, :last_name, :password, :photo, locations_attributes: [:label, :address]])
end
end
DB Schema
ActiveRecord::Schema.define(version: 2019_08_30_001623) do
create_table "locations", force: :cascade do |t|
t.string "label"
t.text "address"
t.float "latitude"
t.bigint "user_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.float "longitude"
t.index ["user_id"], name: "index_locations_on_user_id"
end
create_table "users", force: :cascade do |t|
t.string "email", default: "", null: false
t.string "encrypted_password", default: "", null: false
t.string "reset_password_token"
t.datetime "reset_password_sent_at"
t.datetime "remember_created_at"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "first_name"
t.string "last_name"
t.boolean "admin"
t.text "preference", default: "no preference"
t.integer "default_location"
t.integer "radius"
t.index ["email"], name: "index_users_on_email", unique: true
t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
end
Please let me know if you have any additional question or if you need anymore info.
Appreciate all your helps