If Speech on the Co:Writer iOS App is not working, try sliding the Lock Rotation/Mute switch located on the right hand side of the device to the up position so no Red is showing.
The factory default setting for this switch is Mute function. Launch Co:Writer and test for speech.
If you are on a newer iOS device the Mute option will be in the user Control Center panel. You can bring up this menu by doing a single finger swipe from the bottom of the screen on the device.