UBT error when using IntelISPC in a Plugin

I am trying to get a single .ispc file to build as part of a Project Plugin I am developing against 4.23.
I am basing my method on this, admittedly fairly old, slide: Scalability for All: Unreal Engine* 4 with Intel (Slide 30).
It also seems to be the model used in the Engine for the Chaos, ChaosCore and GeometryCollectionEngine.

I see this error when trying this against both binary distributions of the engine and a full source build…

UnrealBuildTool : error : System.ComponentModel.Win32Exception (0x80004005): The parameter is incorrect
                             at Tools.DotNETCommon.ManagedProcess..ctor(ManagedProcessGroup Group, String FileName, String CommandLine, String WorkingDirectory, IReadOnlyDictionary`2 Environment, Byte] Input, ProcessPriorityClass Priority) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\DotNETCommon\DotNETUtilities\ManagedProcess.cs:line 459
                             at UnrealBuildTool.ParallelExecutor.ExecuteAction(ManagedProcessGroup ProcessGroup, BuildAction Action, List`1 CompletedActions, AutoResetEvent CompletedEvent) in D:\Build\++UE4\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Executors\ParallelExecutor.cs:line 254
                          while launching D:\EpicGamesStore\UE_4.23\Engine\Source\ThirdParty\IntelISPC\bin\Windows\ispc.exe  "E:\Indie\planet 4.23\Plugins\PlanetRenderCore\Source\PlanetRenderCore\Private\PlanetCore\ISPCPlanetMath.ispc" -o "E:\Indie\planet 4.23\Plugins\PlanetRenderCore\Intermediate\Build\Win64\UE4Editor\Development\PlanetRenderCore\ISPCPlanetMath.ispc.obj" --arch=x86_64 --target=avx2,avx,sse4,sse2 -O2 ... 

I am able to run this command line in a shell and generate avx2, avx, sse4 and sse2 .obj files.

Am I missing something? Do I need to do any more than add the IntelISPC module to my plugin and an .ispc file to my source files?

In case this is an issue for anyone else, after updating to the latest version of Visual Studio 2019 and a reboot this now compiles for me.

So this is a problem again with 4.24.3. Am I missing something obvious about DotNet versions, VS versions?