Nested form working in new but not showing up in edit Rails

I'm making a invoice application where i have the @invoice form and inside it i have nested forms for customers, products, and company information. The products form is working fine in all views but the customer form isn't. When i fill in the customer information and create a new invoice it works. But when i try to edit that invoice the entire form is gone.

invoice_form

<%= f.fields_for :customer do |customer| %>
                            <div class="field">
                              <%= customer.label 'Bedrijfsnaam ontvanger' %><br/>
                              <%= customer.text_field :company_name, placeholder: 'bedrijfsnaam', class: 'form-control' %>
                            </div>
                            <div class="field">
                              <%= customer.label 'Adres ontvanger' %><br>
                              <%= customer.text_field :address_line_1, placeholder: 'adres ontvanger', class: 'form-control' %>
                            </div>
                            <div class="field">
                              <%= customer.label 'Postcode & stad' %><br>
                              <%= customer.text_field :zip_code, placeholder: '1234AB Rotterdam', class: 'form-control' %>
                            </div>

Invoices_controller.rb

class InvoicesController < ApplicationController
  before_action :set_invoice, only: [:show, :edit, :update, :destroy]

  # GET /invoices
  # GET /invoices.json
  def index
    @invoices = Invoice.all
  end

  # GET /invoices/1
  # GET /invoices/1.json
  def show
  end

  # GET /invoices/new
  def new
    @invoice = Invoice.new
    @invoice.products.build
    @invoice.build_customer
  end

  # GET /invoices/1/edit
  def edit
  end

  # POST /invoices
  # POST /invoices.json
  def create
    @invoice = Invoice.new(invoice_params)

    respond_to do |format|
      if @invoice.save
        format.html { redirect_to @invoice, notice: 'Invoice was successfully created.' }
        format.json { render :show, status: :created, location: @invoice }
      else
        format.html { render :new }
        format.json { render json: @invoice.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /invoices/1
  # PATCH/PUT /invoices/1.json
  def update
    respond_to do |format|
      if @invoice.update(invoice_params)
        format.html { redirect_to @invoice, notice: 'Invoice was successfully updated.' }
        format.json { render :show, status: :ok, location: @invoice }
      else
        format.html { render :edit }
        format.json { render json: @invoice.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /invoices/1
  # DELETE /invoices/1.json
  def destroy
    @invoice.destroy
    respond_to do |format|
      format.html { redirect_to invoices_url, notice: 'Invoice was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_invoice
      @invoice = Invoice.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def invoice_params
      params.require(:invoice).permit(:number, :currency, :date, :duedate, :btwtotal,
                                      :subtotal, :total, :footer, customers_attributes: [:id, :company_name, :address_line_1, :zip_code, :_destroy],
                                      companies_attributes: [:id, :btw_number, :iban_number, :kvk_number, :company_name, :_destroy],
                                      products_attributes: [:id, :quantity, :description, :unitprice, :btw, :total])
    end
end

Invoice.rb - (model)

class Invoice < ActiveRecord::Base

  has_one :company
  has_one :customer
  has_many :products

  accepts_nested_attributes_for :customer, reject_if: :all_blank, allow_destroy: true
  accepts_nested_attributes_for :products, reject_if: :all_blank, allow_destroy: true
  validates :number, :currency, :date, :duedate, :btwtotal, :subtotal, :total, presence: true

end