If you are not able to get live ads, you have three way to assure getting ads.
1. Enable Test Mode in the AppLovin Dashboard.
Under Monetize > Manage Apps, choose the relevant app and turn on the Test Mode toggle. Note that test mode takes up to 45 minutes to activate and lasts for 2 hours. You should test during that time frame.
2. Turn on Test Mode from the AppLovin SDK.
On recent SDK versions (iOS 3.50+ and Android 6.4.0+), You can turn on test mode within the SDK by modifying the SDK settings. You should make sure to disable test mode before going live and only use that for the test.
Enabling Test Mode in iOS:
ALSdk *sdk = [ALSdk shared]; sdk.settings.isTestAdsEnabled = YES;
Enabling Test Mode in Android:
final AppLovinSdk sdk = AppLovinSdk.getInstance( context );
sdk.getSettings().setTestAdsEnabled( true );
3. Using a VPN to a country with high advertising demand
If you believe the reason you are not getting ads is due to a low advertising demand in your geo location, you can try getting real ads using a VPN connection to a country with a higher advertising demand, for example: the United States.
Note: The above steps will only work if the integration was done correctly. If you are still not able to get ads after following these steps, you might have an integration issue and you should follow the support article here for possible reasons for not getting ads.