System sounds too low to hear on iPad Pro 2018

The audible volume of the keyboard click and other system sounds can be controlled from iPad settings:

Settings > Sounds > [Ringer & Alerts] - slide the slider to the left to reduce the volume of system sounds - and to the right to increase.

You should note that this adjustment affects all system sounds. Many users find that reliably setting the volume level of system sounds is easier - and will remain consistent independent of the main volume control - if you also set the associated Set with Buttons setting to OFF.

To adjust ringtone and alert volume go to Settings > Sounds > Ringtone And Alert Volume and adjust the slider.

If this doesn’t work you can try checking Accessibility settings or Reset Settings.