unity import script error

A scripted importer attempted to register file type ‘uss’, which is handled by a native Unity importer. Registration rejected.
UnityEditor.Experimental.AssetImporters.ScriptedImporter:RegisterScriptedImporters()

A scripted importer attempted to register file type 'uxml', which is handled by a native Unity importer. Registration rejected.
UnityEditor.Experimental.AssetImporters.ScriptedImporter:RegisterScriptedImporters(),

Delete your library folder (with unity closed)…or do a reimport all.