The render pipeline for Unity has changed. The class referenced in the DLL ( UnityEditor.Experimental.Rendering.HDPipeline.HDEditorUtils) is no longer valid and throws an exception when you attempt to import the character following the steps outlined the reallusion documentation. The export does work in earlier versions of Unity that support HDRP. Unity has finalized the HDRP for production now, but the Reallusion Auto Setup Utility references the preview package of HDRP still. Here's the exception status:

TypeLoadException: Could not resolve type with token 01000086 (from typeref, class/assembly UnityEditor.Experimental.Rendering.HDPipeline.HDEditorUtils, Unity.RenderPipelines.HighDefinition.Editor, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null)
RLPlugin.RLEditor.OnPostprocessAllAssets (System.String[] kImportedAsset, System.String[] kDeletedAssets, System.String[] kMovedAssets, System.String[] kMovedFromAssetPaths) (at <ebd3e7ff7281451abb96146f9f827b50>:0)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <437ba245d8404784b9fbab9b439ac908>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <437ba245d8404784b9fbab9b439ac908>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <437ba245d8404784b9fbab9b439ac908>:0)
UnityEditor.AssetPostprocessingInternal.InvokeMethod (System.Reflection.MethodInfo method, System.Object[] args) (at <17b72532ee2c4da1b6f632d3f1705fe0>:0)
UnityEditor.AssetPostprocessingInternal.PostprocessAllAssets (System.String[] importedAssets, System.String[] addedAssets, System.String[] deletedAssets, System.String[] movedAssets, System.String[] movedFromPathAssets) (at <17b72532ee2c4da1b6f632d3f1705fe0>:0)
UnityEditorInternal.InternalEditorUtility:ProjectWindowDrag(HierarchyProperty, Boolean)