If you are unable to connect to the VPN server here are some quick things to consider.
(1) The first thing to do with any error is reboot the computer, router/modem. When internet resumes, test the VPN connection
(2) Type account details don't copy and paste and note the CAPS in the password if any. Sometimes when you copy & paste your password a blank space is added at the end.
(3) Try both L2TP IPsec, PPTP and if applicable
SSTP. With L2TP IPsec you will need to use a preshared key / Shared secret stated in the welcome e-mail.
(4) If you are using a wireless connection, try the connection while connected via a cable directly to the modem.
(5) Please check your firewall software. Disable/configure firewall such as Norton, Zone alarm, onecare by adding the server IP to the "trusted" list. If you are able to connect when the firewall is disabled, set an exception for all traffic to the VPN server IP address. If not sure how to do that, contact us and let us know what program you are using.
(6) If connecting via a router, you should have PPTP Pass-through and IPsec pass-through enabled. By default, it is in most cases.
(7) Some users have found that disabling UAC in Vista suddenly allows the connections to work.
(8) Please ping the VPN server IP Address that you are trying to connect to. Are you able to reach the server?
(9) If it was working before and not anymore, delete the VPN Connection from your computer and recreate it.
(10) If still having issues, it might be wise to try the connection at a different location or on a friends computer at another location. Do not save account username and password on your friends computer.