When you have a sentence or word read back to you, you can’t hear the highlighted text.
First, check your iPad's volume is set sufficiently (press the volume buttons along its edge).
If you still can't hear the speech, your iPad is probably in Silent Mode. This isn't always noticeable, as a muted iPad can still make noise!
To unmute your iPad:
If the Control Center doesn't show the Bell icon, it should be possible to unmute by using your iPad’s side switch.
For more help, please visit getsupport.apple.com.