You would receive the unityplayer.dll file missing error because either it was deleted or the download has pulled down a corrupt version.
The error would appear as this or similar wording.
To resolve this issue
Step 1. Click on this link and install the latest version https://dlldownloads.com/unityplayer-dll/
Step 2. Check your downloads folder and Unzip the newly downloaded unityplayer.zip file.
Step 3. Once unzipped moved the Unityplayer.dll file into vanspace3D folder that you saw it in originally
Step 4. Continue with the downloading process Downloading on Windows