Enum property translation not working

I'm using `Enum` from Geta EPi.Extensions attribute on a block propert, which implement ideas following these blog posts:

http://joelabrahamsson.com/enum-properties-with-episerver/

https://world.episerver.com/Blogs/Linus-Ekstrom/Dates/2014/5/Enum-properties-for-EPiServer-75/

Everything is working fine, except the translations for enum properties are not being picked in the UI.

My enum looks like this:

  public enum BlockColumnCount
    {
        OneColumn = 0,
        TwoColumns = 1,
        ThreeColumn = 2
    }

My property like that:

        [Display(
            Name = "Column count",
            GroupName = SystemTabNames.Content,
            Order = 10)]
        [Enum(typeof(BlockColumnCount))]
        [BackingType(typeof(PropertyNumber))]
        public virtual BlockColumnCount ColumnCount { get; set; }

My localization configuration in web config:

<localization fallbackBehavior="Echo, MissingMessage, FallbackCulture" fallbackCulture="en"><providers><add virtualPath="~/Resources/LanguageFiles"
             name="languageFiles"
             type="EPiServer.Framework.Localization.XmlResources.FileXmlLocalizationProvider, EPiServer.Framework.AspNet"/></providers></localization>

My language file:

<?xml version="1.0" encoding="utf-8" ?><languages><language name="en"><property><enum><blockcolumncount><onecolumn>One Column</onecolumn><twocolumns>Two Columns</twocolumns><threecolumn>Three Columns</threecolumn></blockcolumncount></enum></property></language></languages>

I have the file in the correct localization:

This is how the UI looks - lables from XML file are not showing up.

According to this post, it should work to add /property/enum/<type>/<member> into /languages/language, but it's not working for me and at that point of time I don't have any idea what's going on. Please advise.