That appears to be an issue with either Steam itself, or perhaps the file system (permissions) on your machine.
And, seemingly, that error looks to be with the installer for .NET Framework 4.8 (which is a Microsoft component used by many applications), not VoiceAttack itself.
This would be something to contact Steam about, or perhaps try to find more information about through a search engine.
Could be as simple as clearing out a download cache, or something of that nature.