If VoiceAttack is not starting and there is no message, there is a good chance the error information could be written to a file called, 'VoiceAttackFault.txt'. Take a look at this thread to read about how to access that file:
https://forum.voiceattack.com/smf/index.php?topic=2730.0Think about what may have changed recently on your machine - Have you installed any new software such as an antivirus or internet security app? Sometimes those will interfere with VoiceAttack. It's not normal that VA would just stop working for no reason - something has either changed or has gotten out of sorts on your machine - otherwise, if it was an issue that VA could recover from enough to present a message, there would be a message.
If you find that file and cannot make any sense out of it, you can upload it here.