I don't know how you tried it here I have a sample converted polygon as shown below with different types of land cover types.
![Ed__1-1709917713988.png Ed__1-1709917713988.png](https://community.esri.com/t5/image/serverpage/image-id/97418i0A80ABAABD320FCA/image-size/medium?v=v2&px=400)
Here are the steps I followed to get a polygon NLCD for a specific area
1. Add the raster from the Living Atlas.
2. Right click on it and go to Data > Export Raster > under clipping geometry I selected the study area polygon.
3. Then use raster to polygon to convert the raster you get from step 2 it to a polygon feature class and select ClassName if you are interested in Land Cover Types.
You can then export it as a shapefile if need be
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