If you don't see any ads in your live game, or if they were showing at one point but no longer are, you may be using the wrong Game ID, or you may have run out of available campaigns in your region.
Try the following to solve your problem:
Ensure that your game initializes Unity Ads (see integration documents for the appropriate platform).
Ensure that you're using the correct Game ID (note that these are platform-dependent; double-check that you're not using an iOS ID for an Android build or vice versa).
Wait for Unity Ads to be ready before attempting to show ads (it usually takes a few seconds to cache the ad; until then,
Ensure that your device is connected to the internet.
Please be aware that we cannot guarantee the availability of ads. This is why we provide methods to first check if ads are ready and can be shown.
For most of Europe and North America, ad availability is typically not an issue. In countries where fill may be somewhat limited, the effects of this can be more obvious. For instance, if there are only 12 ad campaigns available in a user's country, they can only see a maximum of 12 ad campaigns in a given period of time.
During development, Unity recommends enabling test mode to ensure you always have test ads available.