Hi,
If you have an active license for the plugin or any theme of those which come with the Smart Product Collections plugin in your account, you should see the plugin in the list or simply choose the theme.
I think, however, that we received a ticket in this regard last week, so please ignore this reply if that was your ticket.
Method not found: 'System.Threading.Tasks.Task`1<Nop.Core.IPagedList`1<Nop.Core.Domain.Catalog.Product>> Nop.Services.Catalog.IProductService.SearchProductsAsync(Int32, Int32, System.Collections.Generic.IList`1<Int32>, System.Collections.Generic.IList`1<Int32>, Int32, Int32, Int32, System.Nullable`1<Nop.Core.Domain.Catalog.ProductType>, Boolean, Boolean, System.Nullable`1<System.Decimal>, System.Nullable`1<System.Decimal>, Int32, System.String, Boolean, Boolean, Boolean, Boolean, Int32, System.Collections.Generic.IList`1<Nop.Core.Domain.Catalog.SpecificationAttributeOption>, Nop.Core.Domain.Catalog.ProductSortingEnum, Boolean, System.Nullable`1<Boolean>)'.