Digital Turbine ad monetization failing: why no impressions?

I am absolutely pulling my hair out with this Digital Turbine SDK integration! We just launched a new app and were counting on Digital Turbine for a significant chunk of our initial ad monetization, but it's been hours, and I'm seeing ZERO impressions. I'm completely stuck and urgently need some expert eyes on this.

Here's the situation: We've integrated the latest Digital Turbine SDK (version 3.x.x) into our Android app. The SDK initializes without any apparent errors, and I can see the logs confirming successful initialization. However, when I try to load an ad, the onAdFailedToLoad callback is consistently triggered, and no ads are ever displayed. The ad space just remains blank.

Things I've already checked and re-checked:

• Verified all necessary permissions in AndroidManifest.xml (INTERNET, ACCESS_NETWORK_STATE, etc.).
• Double-checked the Ad Unit IDs – they match exactly what's in our Digital Turbine dashboard.
• Ensured the SDK is initialized correctly in our Application class's onCreate() method.
• Confirmed that DigitalTurbine.loadAd() is being called before DigitalTurbine.showAd(), and both are on the main thread.
• Tried different ad formats (interstitial, rewarded) – same result across the board.
• Cleared app data/cache, reinstalled multiple times.

The console output consistently shows something like this when trying to load an ad:

D/DigitalTurbineSDK: Initializing SDK with AppId: XXXXX
I/DigitalTurbineSDK: SDK initialized successfully.
D/DigitalTurbineSDK: Attempting to load ad for placement: my_interstitial_placement
E/DigitalTurbineSDK: Ad failed to load for placement: my_interstitial_placement. Error Code: 2003, Message: No Fill.
I/DigitalTurbineSDK: onAdFailedToLoad callback triggered for placement: my_interstitial_placement

That "Error Code: 2003, Message: No Fill" is haunting me. It implies there are no ads available, but we just set up campaigns, and there should be plenty of demand. Is there some specific configuration on the Digital Turbine dashboard I'm missing? Or a common integration gotcha that leads to this "No Fill" error?

I'm at my wit's end here. Any insights, debugging tips, or common solutions for Digital Turbine integration issues leading to "No Fill" would be a lifesaver. Please, someone help me get these ads running! Eagerly awaiting any expert advice!