Error 721 on reliance netconnect data card

I am getting Error 721 on reliance netconnect . A PPP conversation was attempted, but the remote computer did not respond. can some one help me ?

Thanks

Uninstall and re-install driver. To uninstall data card software- Go to Start -> Settings -> Control Panel. Open Add or Remove Programs.

Install data card software- Run the setup file of data card software from the CD & follow the instructions.