If you cannot hear the game sounds through your iPad speakers but they work fine through headphones, here are a few things to try:
1. Restart the iPad
2. Check the bell icon in the control center, and unmute it if it is muted
3. It’s possible your iPad is connected to a Bluetooth device (headphones, speaker, car) or an AirPlay device (Apple TV) and the sound is playing there rather than your iPad’s speakers. To check where sound is playing from, open Control Center on your iPad by double-pressing the Home button or swiping up from below the bottom of the screen with four fingers. Then, press and hold down (force touch) the audio interface box. Next, tap on the AirPlay audio icon — it looks like a triangle with three half circles above it. If it says “Headphones” or the name of one of your Bluetooth devices, then the audio is actually playing somewhere else. Disconnect from that other device, then try to play audio from your iPad’s speaker again.
4. Have a look in settings > sounds and move with the Ringer and Alert volume setting around
5. Sometimes small debris or moisture can get into the headphone jack causing the ipad to think there are headphones plugged in. You can quickly check to see if your iPad is stuck in headphones by pressing the volume buttons again. If the pop-up that appears says “Headphones” rather than “Volume” or “Sounds Effects”, that may be the issue. If so, gently clean it out and try to dry it with a hair dryer for 30 to 60 seconds
6. Some people have had this issue after charging with a different cable/charger that came with the iPad. Try using the original cable/charger that came with the unit.