By default, your iPhone is set to vibrate, whether in ring or silent mode. To confirm this, tap the "Settings" app, followed by "Sound;" you'll see the "Vibration" switch toggled "On" under both "Silent" and "Rings and Alerts." If your device has stopped ringing, you may have inadvertently muted your iPhone's sound, which is set independently of vibration. Inspect and readjust a few hardware and software settings to restore your iPhone's ring.
Check the small "Ring/Silent" switch that's uppermost on your iPhone's left edge. If the switch is flipped towards the back of your device and reveals a red dot or red bar, then your device has been muted. In this mode, iPhone will not make any sound, except for alarms programmed into your "Clock" app. Flip the switch towards the front of your device if you wish to make all ringtones and text tones audible again.
Verify that your iPhone's volume is not turned down. Press the "Volume Up" button that's located right below the "Ring/Silent" switch on your iPhone's left edge. On your screen, you will see a speaker icon and a horizontal bar underneath indicating your current volume level. If volume is set at its lowest setting, your iPhone will still make audible sounds, but so faintly, you may miss it.
To make your device ring louder -- and with conviction -- press and hold the "Volume Up" button until the volume bar reaches a higher level. Next, to ensure that your volume button commands are enforced, tap "Settings" on your home screen followed by "Sounds." Under "Ringer and Alerts," tap to toggle the "Change with Buttons" switch to "On."
Text Tones Deactivated
Tap "Settings," then "Sounds," followed by "Text Tone." You will see list of sound options that you can apply to various contacts, messages, reminders and alerts. If "None" is selected, then silence is your default setting; tap any sound from the list to change this.
When you put your iPhone through the paces for a prolonged period, it can get overwhelmed just like any other computer -- and even some people -- would. Three simple resets may fix your ringing issue. First, reset your ringtone only. Tap "Settings," "Sounds," "Ringtone," and then choose a different ringtone. Second, restart your iPhone. Press and hold the Sleep/Wake button on the top-right edge of your device until the Apple logo appears and your device cycles down. Then wait a few minutes before pressing the button again to turn your device back on and drag the onscreen slider to the right. Finally, perform a hard-reset. Simultaneously press the "Sleep/Wake" button and the round "Home" button below your display for roughly 10 seconds until the Apple logo appears.