Logfile missing?

Since there are very few setting options to adjust, and I'm sure you tried them all as you said, I suspect it stopped working because of a problem during the upgrade itself. Perhaps part of the old version did not get removed during the upgrade process.

I would try a clean reinstall to see if that fixes it. Use the instruction from the Zone Labs website here (link).

But, the main key to a clean uninstall of Zone Alarm is making sure no part of it is running while uninstalling. What I do is I uncheck the "Load Zone Alarm at startup" button in the Overview panel > Preferences tab. Then I exit ZA from the systray icon option Shutdown ZoneAlarm. Then reboot the system. Once booted, I check in the task manager to be sure it is not running. ZA runs in two separate processes: vsmon.exe & zonealarm.exe

If it's not running, use Add/Remove Programs to deinstall. Reboot the system again (I believe it will reboot as part of deinstall itself). Then once booted again, install the new version.

Never attempt to manually remove the ZoneAlarm entry from the Startup folder or kill ZA via the task manager. Let it disable itself from startup using it's built-in options. This has always worked for me and I've installed and deinstalled a whole lot of ZA versions on all kinds of different Windows.

Note that you will have to reset all your configs (trusted zone contents, program settings) following a clean install, so be sure you make note of anything special you have set there.