Am implementing Applovin ads on a mobile app built with flutter. It is my first time to do applovin ads implementation on flutter.

Everything I have setup successfully. Applovin SDK installed and initialized successfully as you can see in the debug console log below. Test mode enabled on the applovin account for testing purposes. Added my device to be able to do testing.

Everything is working successfully as you can see on debug console logs below, only that nothing shows up on my phone screen.

Debug console logs

D/AppLovinSdk(24783): [AppLovinMAX] Initializing AppLovin MAX Flutter v2.0.0...
D/AppLovinSdk(24783): [AppLovinSdk]
D/AppLovinSdk(24783): ========================================
D/AppLovinSdk(24783): SDK Session Begin
D/AppLovinSdk(24783): ========================================
D/AppLovinSdk(24783): [AppLovinSdk]
D/AppLovinSdk(24783): ========================================
D/AppLovinSdk(24783): =====AppLovin SDK=====
D/AppLovinSdk(24783): ===SDK Versions===
D/AppLovinSdk(24783): Version: 11.4.6
D/AppLovinSdk(24783): Plugin Version: Flutter-2.0.0
D/AppLovinSdk(24783): Ad Review Version: 4.5.14
D/AppLovinSdk(24783): OM SDK Version: 1.3.30-Applovin
D/AppLovinSdk(24783): ===Device Info===
D/AppLovinSdk(24783): OS: 12 (S - API 31)
D/AppLovinSdk(24783): GAID: <Enable verbose logging to see the GAID to use for test devices - https://monetization-support.applovin.com/hc/en-us/articles/236114328-How-can-I-expose-verbose-logging-for-the-SDK>
D/AppLovinSdk(24783): Model: Nokia G10
D/AppLovinSdk(24783): Locale: en_US
D/AppLovinSdk(24783): Emulator: false
D/AppLovinSdk(24783): Tablet: false
D/AppLovinSdk(24783): ===App Info===
D/AppLovinSdk(24783): Application ID: ---
D/AppLovinSdk(24783): Target SDK: 30
D/AppLovinSdk(24783): ExoPlayer Version: 2015001
D/AppLovinSdk(24783): ===SDK Settings===
D/AppLovinSdk(24783): SDK Key: ---
D/AppLovinSdk(24783): Mediation Provider: max
D/AppLovinSdk(24783): TG: 1
D/AppLovinSdk(24783): Test Mode On: true
D/AppLovinSdk(24783): Verbose Logging On: false
D/AppLovinSdk(24783): ===Privacy States===
D/AppLovinSdk(24783): Please review AppLovin MAX documentation to be compliant with regional privacy policies.
D/AppLovinSdk(24783):
D/AppLovinSdk(24783): Age Restricted User - No value set
D/AppLovinSdk(24783): Has User Consent - No value set
D/AppLovinSdk(24783): "Do Not Sell" - No value set
D/AppLovinSdk(24783): ========================================

D/AppLovinSdk(24783): [MediationDebuggerListAdapter]
D/AppLovinSdk(24783): ========== MEDIATION DEBUGGER ==========
D/AppLovinSdk(24783): ========== APP INFO ==========
D/AppLovinSdk(24783): Dev Build - true
D/AppLovinSdk(24783): Test Mode - enabled
D/AppLovinSdk(24783): Target SDK - 30
D/AppLovinSdk(24783): ========== MAX ==========
D/AppLovinSdk(24783): SDK Version - 11.4.6
D/AppLovinSdk(24783): Plugin Version - Flutter-2.0.0
D/AppLovinSdk(24783): Ad Review Version - 4.5.14
D/AppLovinSdk(24783): ========== PRIVACY ==========
D/AppLovinSdk(24783): Age Restricted User - No value set
D/AppLovinSdk(24783): Has User Consent - No value set
D/AppLovinSdk(24783): "Do Not Sell" - No value set
D/AppLovinSdk(24783): ========== NETWORKS ==========
D/AppLovinSdk(24783): ---------- APPLOVIN_NETWORK ----------
D/AppLovinSdk(24783): Status  - COMPLETE
D/AppLovinSdk(24783): SDK     - 11.4.6
D/AppLovinSdk(24783): Adapter - 11.4.6
D/AppLovinSdk(24783): ========== AD UNITS ==========
D/AppLovinSdk(24783): ---------- Banner ----------
D/AppLovinSdk(24783): Identifier - ...
D/AppLovinSdk(24783): Format     - BANNER
D/AppLovinSdk(24783): ---------- Interstitial ----------
D/AppLovinSdk(24783): Identifier - ...
D/AppLovinSdk(24783): Format     - INTER
D/AppLovinSdk(24783): ---------- Native ----------
D/AppLovinSdk(24783): Identifier - ...
D/AppLovinSdk(24783): Format     - NATIVE
D/AppLovinSdk(24783): ========== END ==========

D/AppLovinSdk(24783): [AppLovinMAX] Creating BANNER with ad unit id "--" and position: "bottom_center"
D/AppLovinSdk(24783): [AppLovinMAX] Showing BANNER with ad unit id "--"

This is how am loading the banner ad

final String _banner_ad_unit_id = "--";

void initializeBannerAds()
 {
    // Banners are automatically sized to 320x50 on phones and 728x90 on tablets
    AppLovinMAX.createBanner(_banner_ad_unit_id, AdViewPosition.bottomCenter);
 }

 initializeBannerAds();  

 AppLovinMAX.showBanner(_banner_ad_unit_id);

So what might be the issue why the ads on debug console are loading and showing successfully while on phone screen there is nothing ?