Oops! Can't hear the Osmo games? There are a few ways to enable/disable the sound on an app on the iPad.
Please first check the side switch (the slider on the top right of more recent iPads). If it is configured to mute and the orange is visible on the slider, then the sound is muted. Interestingly, not all apps respect this setting, so that can explain cases where only Osmo apps seem to be muted.
You can also, inside of any app, verify the sound is turned on in software using the control center.
There should be a volume slider on control center. If that is up and the mute isn't turned on, you should be hearing sound.
If neither was the problem, you can try plugging in headphones to see if you can hear sound on Osmo apps as well as other apps.