Q: I have recently updated the operating system on my iPad. Now my alarm is silent and my FaceTime doesn't ring aloud when a call comes in. How do I fix this please?

Do you see a half moon icon in the upper right corner of the screen? If so, you have Do Not Disturb enabled. Settings>Do Not Disturb. Turn it off.

Or do you have system sounds muted?

System sounds can be muted and controlled two different ways. The screen lock rotation can be controlled in the same manner as well.

Settings>General>Use Side Switch to: Mute System sounds. If this option is selected, the switch on the side of the iPad above the volume rocker will mute system sounds.

If you choose Lock Screen Rotation, then the switch locks the screen. If the screen is locked, you will see a lock icon in the upper right corner next to the battery indicator gauge.

If you have the side switch set to lock screen rotation then the system sound control is in the control center. Swipe up from the bottom of the screen to get to control center. Tap on the bell icon and system sounds will return.

If you have the side switch set to mute system sounds, then the screen lock can be accessed in the same manner as described above.

This support article from Apple explains how the side switch works.

About the iPad Side Switch - Apple Support