When the connect fails and you are prompted to type in the Username / Password credentials again.

A few simple checks will tell you the reason for this:

1. Check your Expiry date in Members Area, make sure that the the Account is still active and has not expired. If expired, the expiry date will show up in red letters. The date format is YY.MM.DD

2. If you switched before, download the config file again just to be sure. Usually you do NOT need to re-download the config file, if so, the members area would automatically prompt the download, but in the case of an AUTH failure, it is a good idea to re-download the config file just to be sure.

3. In the OpenVPN tray, hit the "Edit Config" button of the Account you are trying to connect to and compare these details with your "YourUsername.ovpn" file located in the 'Config' folder of OpenVPN. To do this, open the "YourUsername.ovpn" file with a text editor. Both must contain the exact same parameters. 

4. Important: Compare your connection IP to the one assigned in the members area. In order to do this check your OpenVPN connection log, click the OpenVPN tray icon and choose "View Log" and take a look at an entry which looks similar to this:

   [server] Peer Connection Initiated with [AF_INET]81.95.XXX.XX:1194
   
   Now compare this IP with the assigned IP in your members area, if the IP is not the same then the validation will fail. This can be related to a slow DNS resolving on your side, if the IP differs and if a slow DNS is the reason for             this, then you can simply hardcode the IP in your config file like described here