Make windows TTS working - D9F6EE60-58C9-458B-88E1-2F908FD7F87C Class not registered

[Costas]

An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in System.Speech.dll

Additional information: Retrieving the COM class factory for component with CLSID {D9F6EE60-58C9-458B-88E1-2F908FD7F87C} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG)).

On another Windows machine that TTS is working, go to
%WINDIR%\system32\Speech\Common
transfer the sapi.dll to non working machine to same location.

open cmd on Common folder and registered the dll with :

regsvr32.exe sapi.dll

Depending on sapi.dll architecture (x86/x64) you need the needed /client TTS application/ (x86/x64).

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If you are on Visual Studio and using SpeechSynthesizer (find voices installed), use
Project Properties > Build >Platform target

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Folders :
Speech_OneCore : Contains Microsoft built-in voices. (aka HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SPEECH_OneCore\Voices\Tokens)
Speech : May contain voices installed by third-party applications or software. (aka HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Speech\Voices\Tokens)

Voices get registered under mention registry locations. To find where the actual voice files are, redirect to voice CLID written on registry