The problem you describe indicates that the Quintum is not connecting with the TFTP server hence it asks you to re-enter the PIN repeatedly. You need to establish in your quintum config that you have the correct IP of the voicemaster, then you need to make sure that you have the IP of the quintum register as an endpoint in the voicemaster from Route Management=>Gateways.
If you have the lastest version of the Voicemaster OS, from Reports=>Real-Time Logs=>Radius Log you should be able to monitor radius activity dumps.
If you have another PC, just install a freeware TFTP server and point your Quintum to that IP and that is another way to solve you problem