If ads are not working, please try the below steps.

For Android:

1. Go to Settings > Google > Ads.
2. Tap on Reset advertising ID.
3. Restart your device.
4. You may need to repeat this process a few times until ads start working again.

For iOS:

1. Go to Settings > Privacy & Security > Tracking.
2. Make sure “Allow Apps to Request to Track” is turned ON.
3. Then go to Settings > [game name] and ensure tracking is enabled for the app.
4. Go to Settings > Screen Time > Content & Privacy Restrictions and check that ad-related settings aren't restricted.
5. Restart your device.

Note: If ads still don’t appear, it may be due to temporary ad limits or availability from the ad provider.