InMobi mediation setup help?

hi everyone, i'm super new to mobile ad integration and trying to get inmobi ads working in my android app. i saw the previous thread about sdk integration failing, and i think i got past that part, but now i'm stuck with ads just not showing up at all.

i've followed the basic steps in the inmobi docs for android sdk setup. i added the dependencies, updated my manifest, and put in the basic code to request and show an interstitial ad. i'm using their example ad unit id for testing. when i run the app, there are no errors crashing it, but the ad never loads or shows.

i've tried:

• checking my internet connection (it's fine)
• making sure the ad unit id is correct
• double-checking the manifest permissions (internet, access_network_state)
• calling InMobiSdk.init() in my Application class

i'm expecting the onAdLoadSucceeded callback to fire, but it just doesn't. my logcat shows something like this:

06-07 10:30:15.123 1234-5678/com.example.myapp D/InMobi: InMobiSdk initialized successfully.
06-07 10:30:15.456 1234-5678/com.example.myapp I/InMobi: [InMobi] Ad request successful but no ad available. Error code: 204

that "error code: 204" looks suspicious, but i'm not sure what it means or how to fix it when trying to implement inmobi mediation. what am i missing in my setup for ads to actually show up?