VP4 has gone to a launcher program for more reliable critical file updating. It is possible that a firewall or anti-virus could block launcher.exe. So if you can't run put in an exception in your firewall/anti-virus for launcher.exe in the VP4 directory.
You can always fix any corrupt installation by reinstall.
Get the new installer from vponline.celeris.com, DOWNLOADS on the nav bar, then download and re-install, if you have Full version (offline and online) select Download Full 126.96.36.199, if online only select Virtual Pool 4 Online Download.
For Steam, Exit Steam, restart steam client, click Play to get update.
July 13, 2017