IList property doesn't work in several layers

    [ContentType]
    public class FooterCategory : BlockData
    {
        [Display(
        GroupName = SystemTabNames.Content,
        Name = "Titel",
        Description = "Titel för kategori",
        Order = 100)]
        public virtual string? Title { get; set; }
        [Display(
        GroupName = SystemTabNames.Content,
        Name = "Sektioner",
        Description = "Dela upp kategorin i flera sektioner",
        Order = 120)]
        public virtual IList<FooterSection>? Sections { get; set; }
    }

    [ContentType]
    public class FooterSection : BlockData
    {
        [Display(
        GroupName = SystemTabNames.Content,
        Name = "Titel",
        Description = "Titel för sektion (valfri)",
        Order = 100)]
        public virtual string? Title { get; set; }
        [Display(
        GroupName = SystemTabNames.Content,
        Name = "Rader",
        Description = "Rader",
        Order = 120)]
        public virtual IList<FooterRow>? Rows { get; set; }
    }

    [ContentType]
    public class FooterRow : BlockData
    {
        [Display(
        GroupName = SystemTabNames.Content,
        Name = "Titel",
        Description = "",
        Order = 100)]
        public virtual string? Title { get; set; }
        [Display(
        GroupName = SystemTabNames.Content,
        Name = "Url",
        Description = "",
        Order = 120)]
        public virtual Url? Url { get; set; }
    }

[Display(
Name = "Kategorer i sidfot",
GroupName = TabNames.Footer,
Order = 310)]
public virtual IList<FooterCategory>? FooterCategories { get; set; }

{
  SiteConfigurationPage(locale: sv) {
    items {
      Name
      FooterCategories {
        Title
        Sections {
          Title
        }
      }
    }
  }
}