Why can't I hear my alert sounds or ringer? For some reason, the sounds for ringers, and alerts/notifications on my mother's iPhone appear to not be playing anymore.  Even though the ringer volume in settings is turned up almost to the max, the phone still only vibrates when receiving a call.  And when the phone is placed onto it's charging dock, instead of BEEP ing like it normally does, it simply vibrates.

Interestingly, when I fiddle with the ringer volume slider in settings, the test ringtone plays just fine, and music audio can also be played through the built in speaker.

What's going on?
I would first check to see if the silent switch on the phone, above the volume buttons, is active. That would cause the issue. If that's not the case (the switch is off), I would try powering the phone down (hold down power button at top, then slide to power off), then restarting it.