I checked, and got the same hash as you. Zein, one of the developers, had the same result. The file size here is 9 kb as well, so I suppose the size difference is only there because the version of the game in the demo is an older one.
I’ve uploaded the plugin, if you’d like to replace it and test if something changes. But it seems to be the same one. https://cloud.owncube.com/s/Bw2Bi43jZMziGoZ
Most people who have reported this mentioned they’d recently freshly installed Windows, but I don’t see how that could be the problem, unless Microsoft no longer ships some SAPI components with Windows 10 that it once used to. The required dependencies are kernel32.dll, ole32.dll and msvcr120.dll. But so far people we’ve asked about this do have those files, and I assume you will, too.
Sorry to sound like a Microsoft support person, but … could you try to perform a system check? Unfortunately, it’s not as simple as typing system.check in the console, but for a Microsoft help guide, this is surprisingly useful: https://support.microsoft.com/en-us/help/929833/use-the-system-file-checker-tool-to-repair-missing-or-corrupted-system