Yes, ZoneAlarm free is blocking your VPN and will never tell you.
You were thinking that your VPN server is offline, or worse, your VPN configuration might be gone, considering that you are the only one complaining about this, in fact it is the ZoneAlarm.
To solve this, double click your ZoneAlarm tray icon, hit View details button in Firewall (middle section), click Basic Firewall where is says 7543991 access atempt blocked and in the Log viewer is your VPN server (IP or name)!
Highlight it, click the now enabled button Add to zone, usually the dialog displays Zone: trusted, the IP address, you have to add a coment, or description to this zone to be able to add this enabled access zone.
Hit OK and there you are, your VPN is working again!
While ZoneAlarm never told you about your VPN connection – which is supposed to pay your monthly salary, from which you would upgrade to paid variant of ZoneAlarm (if ever you might be still considering after cutting yourself from work), it is still suggesting you to upgrade now…