I have found a solution that worked for me without restarting (although restarting worked before when this happened)
My problem was that both the
Hot Key or the contextual menu
Start Speaking did not work within any application like
When I went to
System Preferences ->
Play the button toggled to
Stop as if playing but I heard no audio.
My Solution: I switched my default voice from Heather Infovox iVox HQ to Samantha then pressed the
I got audio.
Then I switched back to Heather and both
Hot Key and contextual menu
Start Speaking worked without quitting any apps or restarting my computer.