How To Install the WiX Installer Extensions for VS2017

I'm hoping that someone out there might be able to enlighten me as to what is happening with my attempts to install the WiX VS2017 Extensions. When I attempt to install via the VS2017 Extension manager the process fails. The follow is content from the associated error log:

23/07/2019 11:58:02 - Command line parameters:
23/07/2019 11:58:02 - C:\Program Files (x86)\Microsoft Visual Studio\2017 \Professional\Common7\IDE\vsixinstaller.exe,/appidinstallpath:C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\IDE\devenv.exe,/skuName:Pro,/skuVersion:15.0.27428.2015,/appidname:Microsoft Visual Studio Professional 2017,/culture:en-US,C:\Users\TE602510\AppData\Local\Temp\VSIXl4vrmrr1.vsix
23/07/2019 11:58:02 - -------------------------------------------
23/07/2019 11:58:02 - Microsoft VSIX Installer
23/07/2019 11:58:02 - -------------------------------------------
23/07/2019 11:58:05 - Initializing Install...
23/07/2019 11:58:05 - Extension Details...
23/07/2019 11:58:05 -   Identifier         :  WixToolset.VisualStudioExtension.Dev15
23/07/2019 11:58:05 -   Name               : Wix Toolset Visual Studio 2017 Extension
23/07/2019 11:58:05 -   Author             : WiX Toolset
23/07/2019 11:58:05 -   Version            : 1.0.0.4
23/07/2019 11:58:05 -   Description        : Visual Studio integration for the WiX Toolset - the most powerful set of tools available to create your Windows installation experience.
23/07/2019 11:58:05 -   Locale             : en-US
23/07/2019 11:58:05 -   MoreInfoURL        : http://wixtoolset.org/
23/07/2019 11:58:05 -   InstalledByMSI     : False
23/07/2019 11:58:05 -   SupportedFrameworkVersionRange : [4.0,)
23/07/2019 11:58:05 - 
23/07/2019 11:58:07 -   SignatureState     : ValidSignature
23/07/2019 11:58:07 -   SignedBy           : WiX Toolset (.NET Foundation)
23/07/2019 11:58:07 -   Certificate Info   : 
23/07/2019 11:58:07 -       -------------------------------------------------------
23/07/2019 11:58:07 -       [Subject]       : CN=WiX Toolset (.NET Foundation), O=WiX Toolset (.NET Foundation), L=Redmond, S=wa, C=US, SERIALNUMBER=603 389 068
23/07/2019 11:58:07 -       [Issuer]        : CN=.NET Foundation Projects Code Signing CA, O=.NET Foundation, C=US
23/07/2019 11:58:07 -       [Serial Number] : 0D5EF90303C2280377DFE04D74E20861
23/07/2019 11:58:07 -       [Not Before]    : 03/04/2019 01:00:00
23/07/2019 11:58:07 -       [Not After]     : 07/04/2022 13:00:00
23/07/2019 11:58:07 -       [Thumbprint]    : C95FC39334E667F3DD3D82AF382E05719B88F7C1
23/07/2019 11:58:07 - 
23/07/2019 11:58:07 -   Supported Products : 
23/07/2019 11:58:07 -       Microsoft.VisualStudio.Community
23/07/2019 11:58:07 -           Version : [15.0,16.0)
23/07/2019 11:58:07 - 
23/07/2019 11:58:07 -   References         : 
23/07/2019 11:58:07 -       -------------------------------------------------------
23/07/2019 11:58:07 -       Identifier   : WixToolset.VisualStudioExtension.Schemas3
23/07/2019 11:58:07 -       Name         : WiX Toolset v3 Schemas for Visual Studio
23/07/2019 11:58:07 -       Version      : 
23/07/2019 11:58:07 -       MoreInfoURL  : 
23/07/2019 11:58:07 -       Nested       : Yes
23/07/2019 11:58:07 - 
23/07/2019 11:58:07 -       -------------------------------------------------------
23/07/2019 11:58:07 -       Identifier   : WixToolset.VisualStudioExtension.Schemas4
23/07/2019 11:58:07 -       Name         : WiX Toolset v4 Schemas for Visual Studio
23/07/2019 11:58:07 -       Version      : 
23/07/2019 11:58:07 -       MoreInfoURL  : 
23/07/2019 11:58:07 -       Nested       : Yes
23/07/2019 11:58:07 - 
23/07/2019 11:58:07 -   Prerequisites      : 
23/07/2019 11:58:07 -       -------------------------------------------------------
23/07/2019 11:58:07 -       Identifier   : Microsoft.VisualStudio.Component.CoreEditor
23/07/2019 11:58:07 -       Name         : Microsoft.VisualStudio.Component.CoreEditor
23/07/2019 11:58:07 -       Version      : [15.0,16.0)
23/07/2019 11:58:07 - 
23/07/2019 11:58:07 - Signature Details...
23/07/2019 11:58:07 -   Extension is signed with a valid signature.
23/07/2019 11:58:07 - 
23/07/2019 11:58:07 - System.IO.FileLoadException: Could not load file or   assembly 'Microsoft.VisualStudio.Threading, Version=15.5.0.0,  Culture=neutral,   PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly   reference. (Exception from HRESULT: 0x80131040)
File name: 'Microsoft.VisualStudio.Threading, Version=15.5.0.0,  Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
   at VSIXInstaller.SupportedVSSKU.get_Host()
   at VSIXInstaller.SupportedVSSKU.CreateExtensionEngine()
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.LazyInitValue()
   at System.Lazy`1.get_Value()
   at VSIXInstaller.App.GetExtensionEngineForApplicableSKU(SupportedVSSKU supportedSKU, IInstallableExtension installableExtension, List`1 applicableSKUs, Boolean isRepairSupported)
   at VSIXInstaller.App.GetInstallableData(String vsixPath, Boolean isRepairSupported, IEnumerable`1& skuData)
   at VSIXInstaller.App.Initialize(Boolean isRepairSupported)
   at VSIXInstaller.App.Initialize()
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()

VS2017 Is a completely fresh install and as far as I can see was completely successful. After installing VS2017, I immediately went to the VS Extension Manager and selected the WiX Installer Extension. On closing VS as instructed, the above error was generated. Install was carried out as administrator.