Hello,
It looks like somehow gem's active record extension hasn't been extended into your ActiveRecord::Base yet. Does Product.ancestors include SeemsRateable::Models::ActiveRecordExtension::Rateable ?
I'll try to look deeper into the issue later.
Thanks for the feedback!

It's not there. Here is a dump of Product.ancestors -

=> [Product(id: integer, name: string, description: text, available_on: datetime, deleted_at: datetime, slug: string, meta_description: text, meta_keywords: string, tax_category_id: integer, shipping_category_id: integer, created_at: datetime, updated_at: datetime, avg_rating: decimal, reviews_count: integer, asset_file_name: string, asset_content_type: string, asset_file_size: integer, asset_updated_at: datetime, category_id: integer, supplier_sku: string), Product::GeneratedAssociationMethods, Kaminari::ConfigurationMethods, Kaminari::ActiveRecordModelExtension, #Module:0x00000002ac4c00, ActiveRecord::Base, Paperclip::Schema, Paperclip::Validators::HelperMethods, Paperclip::Validators, Paperclip::Callbacks::Running, Paperclip::Callbacks, Paperclip::Glue, Kaminari::ActiveRecordExtension, CanCan::ModelAdditions, PaperTrail::Model, ActiveRecord::Store, ActiveRecord::Serialization, ActiveModel::Serializers::Xml, ActiveModel::Serializers::JSON, ActiveModel::Serialization, ActiveRecord::Reflection, ActiveRecord::Transactions, ActiveRecord::Aggregations, ActiveRecord::NestedAttributes, ActiveRecord::AutosaveAssociation, ActiveModel::SecurePassword, ActiveRecord::Associations, ActiveRecord::Timestamp, ActiveModel::Validations::Callbacks, ActiveRecord::Callbacks, ActiveRecord::AttributeMethods::Serialization, ActiveRecord::AttributeMethods::Dirty, ActiveModel::Dirty, ActiveRecord::AttributeMethods::TimeZoneConversion, ActiveRecord::AttributeMethods::PrimaryKey, ActiveRecord::AttributeMethods::Query, ActiveRecord::AttributeMethods::BeforeTypeCast, ActiveRecord::AttributeMethods::Write, ActiveRecord::AttributeMethods::Read, #Module:0x00000004607008, ActiveRecord::AttributeMethods, ActiveModel::AttributeMethods, ActiveRecord::Locking::Pessimistic, ActiveRecord::Locking::Optimistic, ActiveRecord::CounterCache, ActiveRecord::Validations, ActiveModel::Validations::HelperMethods, ActiveSupport::Callbacks, ActiveModel::Validations, ActiveRecord::Integration, ActiveModel::Conversion, ActiveRecord::AttributeAssignment, ActiveModel::ForbiddenAttributesProtection, ActiveRecord::Sanitization, ActiveRecord::Scoping::Named, ActiveRecord::Scoping::Default, ActiveRecord::Scoping, ActiveRecord::Inheritance, ActiveRecord::ModelSchema, ActiveRecord::ReadonlyAttributes, ActiveRecord::NoTouching, ActiveRecord::Persistence, ActiveRecord::Core, Object, HomeHelper, PP::ObjectMixin, ActiveSupport::Dependencies::Loadable, JSON::Ext::Generator::GeneratorMethods::Object, Kernel, BasicObject]

Is there a chance that you will get to this sooner else, I will try finding something else. Please do let me know.

I appreciate all your work on this plugin

I guess the problem is somewhere in the initialization order. I looks like

module SeemsRateable
  class Engine < ::Rails::Engine
    isolate_namespace SeemsRateable

    initializer :seems_rateable do
     ::ActiveSupport.on_load(:active_record) { extend SeemsRateable::Models::ActiveRecordExtension }

is executed after the loading of ActiveRecord. I'm still working on it so for the time being feel free to migrate to another solution.

I'll try to let you know If I make any progress.

Anyways, thanks for the feedback!