No sounds
I Can't reduce or increase the volume. when operating the volume control button on side, it displays as"sound effect" but doing nothing.
iPad
Go to Settings>Sounds>Ringers and Alerts>Change with buttons>Off. Make sure that you do not have system sounds muted as well.
If you have an older iPad, see this for help with unmuting system sounds.
About the iPad Side Switch - Apple Support
IF you have one these iPads, look at this.
Turn on Mute and Orientation Lock on iPad Pro, iPad Air 2, or iPad mini 4 - Apple Support