Hi! I see you're having trouble with no sound in the MON app on your iPhone running iOS 18.5. Let's get to the bottom of this together.

First, just to clarify:
- Is the sound issue happening only with the MON app, or is your iPhone not producing any sound in other apps as well?
- Have you noticed if the device is on silent mode or if the volume is low?
- Did this problem start recently, perhaps after an update or a change in settings?

Meanwhile, here are a few simple steps we can try to fix the no sound issue in the MON app:

1. Check the Mute Switch and Volume
- On the side of your iPhone, make sure the mute switch (above the volume buttons) is not turned on (orange visible means mute).
- Press the volume up button to increase the sound level.

2. Check App Sound Settings
- Open the MON app and see if there is an in-app volume or sound setting that might be muted.

3. Restart the MON App
- Double press the Home button or swipe up from the bottom to access the app switcher.
- Swipe the MON app off the screen to close it.
- Reopen the MON app and test sound again.

4. Restart Your iPhone
- Sometimes a simple restart clears minor glitches. Hold the side button and either volume button until the "slide to power off" appears.
- Turn off the device, wait 30 seconds, then power back on.

5. Check Bluetooth and Headphones
- Go to Settings > Bluetooth and make sure your iPhone isn’t connected to any Bluetooth audio devices (which might be playing sound elsewhere).
- Disconnect them or turn Bluetooth off temporarily.

6. Ensure “Silent Mode” is Off in Control Center
- Swipe down from the top right corner (on iPhone X or later) or up from the bottom (on earlier models) to open Control Center.
- Check if the bell icon (Silent mode) is turned off.

If you’ve tried these steps or if the sound issue persists only in the MON app, we can dig a little deeper. Let me know what you find, and we’ll continue troubleshooting!

Are you okay with trying these steps first?