Voice navigation not starting

Recently the voice navigation has failed to start after entering a destination (a previous destination, a set destination, or a new one). Once hitting "Go To" I expect the route to be calculated and the voice guidance to begin as normal, but something prevented it. Shutting off and restarting the car seemed to resolve it, then it occurred days later. I've searched the threads but mostly found responses to how to update the maps.

This is a 2010 Gen 3. Any assistance appreciated!

 

I can't recall the exact unfolding of events while using navigation, whether as normal or in this last development, but I believe even the screen was not showing the guidance according to the input destination after commencing. But, yes, there's a chance it's been muted, though I'm not aware of such a button. Where is it? Thank you —

 

It's a 2010 Gen 3. I've combed through the menus and guide on many an occasion without seeing it. Someone here will likely know.