Problem Description
About 3 months after launching the app, I discovered that AdMob ads were not displaying properly. Test ads worked normally, but when testing with actual ad IDs, the following error occurred:
Error Domain=com.google.admob Code=1 "Request Error: No ad to show."Despite waiting several days, the situation didn’t improve. The AdMob console showed requests being recorded normally, but impressions remained at 0.
Initial Approach
Initially, I took the “no ad to show” message at face value and considered adding mediation. However, it seemed strange that this phenomenon persisted for several days when the current traffic wasn’t particularly high.
After searching through Reddit posts and other developer blogs, I found that many people had similar experiences. In most cases, “silent policy violations” were the cause, and test device registration was commonly recommended.
Solution Attempt: Test Device Registration via IDFA
To solve the problem, I tried to register as an AdMob test device, which required the IDFA value. IDFA (Identifier for Advertisers) is a unique identifier used for ad tracking on iOS, and user consent has been required since iOS 14.
To register team members’ devices as test devices as well, I created a View to check the IDFA as follows:
import SwiftUI
import AdSupport
struct GetIDFAView: View {
var body: some View {
let idfa = ASIdentifierManager.shared().advertisingIdentifier.uuidString
ZStack {
Text("\(idfa)")
}
}
}
#Preview {
GetIDFAView()
}If the IDFA value appears as all zeros like 00000000-0000-0000-0000-000000000000, you need to enable the toggle in iPhone Settings: Settings → Privacy & Security → Tracking → Select App or Settings → Apps → Select App → Allow Tracking.
The obtained IDFA value can be registered in the Google AdMob console by navigating to Settings → Test Devices → Add Test Device.
Results
When test devices are properly registered, you can see the “Test mode” text even in actual ads as shown above.
The timeline was as follows:
- July 15th: Ad impressions suddenly stopped (only requests, 0 impressions)
- July 19th: Registered IDFA as test device
- July 21st: Ad impressions resumed
While the exact causal relationship isn’t clear, ads started showing again just two days after test device registration. Since this problem occurred without receiving any penalty messages or warnings from AdMob, I plan to register test devices from the development stage in future projects.