Go to setting - apps - push the 3 dots in the right hand corner- click app permissions - then microphone- three dots in the corner again - click on show system - scroll down to Samsung voice input and turn on. Should start working
There's one more thing you can do. Settings / general management /language and input /turn on keyboard button. When you open the keyboard an icon on the right side of the navigation bar will open a pop-up menu that lets you select between Google voice typing and Samsung voice input. If you have 2 keywords installed you can switch between them. I'm using SwiftKey as the default and it uses Google voice typing as the default for voice to text. It's nice to be able to use both voice inputs and keyboards to see which one is more accurate.
There is also another way that I just found out you need to have the Google app on your phone enabled. The app comes with your phone so all you have to do is go on your apps and enable it. And then you will see it pops up on your keyboard.