If your iPhone or iPad has no sound, here are some things you can try to troubleshoot the issue:

1. Check the volume: Make sure the volume is turned up. You can also try adjusting the volume using the buttons on the side of the iPhone or in the Control Center.
   
2. Check the mute switch on the side of your device. When you mute your device, you won’t hear any sound from the app. Even if the built-in apps have sound, the device may be muted. If your device has a switch on the side:
   1. Check if a red dot is visible within the switch. If so switch the knop in the opposite direction.
   2. Change the volume with the two buttons on the side of your device.

   If your device does not have a switch on the side or the side switch is set to Orientation Lock:

   1. Swipe up along the bottom of the screen to display Control Center. You can do this from any screen, including the Lock screen.
   2. Tap the Mute button.
   3. The Mute button will appear highlighted when it’s on. Make sure it’s not highlighted.
   4. Change the volume with the two buttons on the side of your device.
   
   
3. Turn off any Focus modes. Apple's Do Not Disturb includes a sometimes confusing array of so-called Focus modes which can minimize distractions when you're trying to get work done. But it can also sometimes be confusing and prevent sound from playing when you expect it to. 
   1. Swipe up along the bottom of the screen to display Control Center. You can do this from any screen, including the Lock screen.
   2. Check the Focus icon.
   3. If it says anything other than Focus, tap the icon to turn it off. 
   
   

4. Make sure audio isn't being routed to a nearby Bluetooth device. Your iPhone may be connected to a Bluetooth audio device like a Bluetooth speaker or earbuds that are too far away to hear.

   1. Swipe up along the bottom of the screen to display Control Center. You can do this from any screen, including the Lock screen.
   2. Tap the Bluetooth icon to turn off the Bluetooth radio. That will release any Bluetooth devices and force the iPhone to use its built-in speaker. 
   
   
5. Restart the device: A simple restart can often resolve many software issues. To restart your iPhone, press and hold the power button until the "slide to power off" option appears. Swipe the power icon to the right to turn off the iPhone, and then press and hold the power button again to turn it back on.
   

6. Check the sound settings: Go to Settings > Sounds & Haptics and make sure that the volume is turned up for ringtones, alerts, and other sound options.

7. Check for headphone connectivity: If you have headphones or earbuds plugged in, try unplugging them to see if the sound returns.

8. Check for any software updates: Make sure that your iPhone is running the latest software updates, as this can often fix bugs and issues that affect the sound.

9. Reset all settings: If none of the above solutions work, you can try resetting all settings on your iPhone. Go to Settings > General > Reset > Reset All Settings. This will reset all settings on your iPhone but will not delete any of your data.

If none of these solutions work, you may want to contact Apple Support or visit an Apple Store for further assistance.