カラムを追加後にApplicationContorllerを変更

class ApplicationController < ActionController::Base
  before_action :configure_permitted_parameters, if: :devise_controller?

  protected
    def configure_permitted_parameters
      added_attrs = [ :email, :admin, :password, :password_confirmation ]
      devise_parameter_sanitizer.permit :sign_up, keys: added_attrs
      devise_parameter_sanitizer.permit :account_update, keys: added_attrs
      devise_parameter_sanitizer.permit :sign_in, keys: added_attrs
    end
end

参考記事

https://qiita.com/ryutaro9595/items/985ade15b5316e4cad82

https://qiita.com/hz1_d/items/77e440b09a1ddbe56263