VPN

Hi, I have got 5 dedicated ip addresses i could use on the server. My server on which i have setup VPN gets the IP address from my service provider dynamically, although the IP address always remain same. My VPN clients are unable to sign in to the server when they dial in to the server’s main IP, but if they use any other virtual IP they are able to logon. The virtual ip are binded to my internal network card. Can anyone suggest me what should i do to get my clients connected to the server IP rather than the virual IP’s?

Regards.