Please try resetting your "Ad ID" settings for Android devices:
- Open your phone settings
- Find "Google", then click on it
- Click "Ads"
- Click Reset Advertising ID, then click OK.
If you have an Apple device please make sure your iOS is the latest version first, if it doesn't solve the issue please try the following:
- Check that ATT is not disabled for all applications in the iOS settings.
- Delete the game.
- Download the game, provide the ATT consent.
- Check if the network is available and stable.
- Optional for China's residents: Enable VPN.
- Launch the game.
- Accept or reject AdMob consent.
Make sure your email address matches your MW email address.
If this does not help, then there are no ads, or it is not available in your region at the moment.
You may also try to use a VPN.