[GIS] Unique value symbology not loading although values exist in ArcGIS raster attribute table

arcgis-desktoparcmaprastersymbology

I have a weird problem. I have a feature class generated from processing multiple rasters and converted by Raster to polygon tool in ArcGIS 10.4.

I would like to apply Unique value symbology based on field gridcode in ArcMap.
The individual gridcode values (from 0 to 14) exist in the field gridcode in Attribute table, I can also Label them, as here:

Unique labels of gridcode

However, when I want to apply Unique value symbology, only the value "1" gets load after "Add all values".

After loading "Add all values" symbology, the unique values are not loaded

Do you know why the other values do not get loaded?

Best Answer

My problem consisted in a fact, that I had two fields in the attribute table with same alias: gridcode. (even if the Field names were different: gridcode and gridcode_1)

When I have modified the alias of one of those (gridcode -> gridcode_1), then it magically worked!

My answer is based on comments of @BERA, published here: Two fields have same name in attribute table and not possible to get unique values?

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