Prius (2010-12) :: Voice Guidance Stopped Working

I bought the 2012 Prius three in Apr, and the navigation was working fine, when i entered a destination. When I entered a destination, it would say, "Please drive to the highlighted route" and it would tell the turn by turn directions and in case you miss the turn, it will immediately say "Route Recalculation" and then guide you to the next turn.

Somehow this stopped working and there is no voice guidance!!! Now when I enter the a destination, it will not say anything. If you are driving in the right direction, no turn by turn voice guidance. If you miss the turn, then it will say "calculating the route". This is driving me nuts since 2-3 weeks. I must have pressed some button or deactivated it unknowingly.

I took it to the dealer and the service technician could not figure it out. They said that they have to call the Toyota Technical Service to find out ( looks like only they can call, not the owner).

They said they tried to reset it to the factory setting, but that didn't work. Not sure if they know what they are doing. I think these technicians are mechanics, but not familiar with the software and the electronic components and their operation.