Step 7: Testing & troubleshooting

Testing

You can use your real API key from the start — there is no separate sandbox key.

1. Register your site URL in the dashboard (exact domain match required).
2. Deploy your React app to that domain (not localhost).
3. Open browser DevTools → Console.
4. Click your ad trigger.
5. You should see the lifecycle in order: loaded → started → firstQuartile → midpoint → thirdQuartile → complete.

For React Native, run on a device/simulator with the WebView pointed at your deployed https:// page, and watch the JS console (Flipper, Safari Web Inspector for iOS, or chrome://inspect for Android) for the same sequence.

Troubleshooting

Symptom in the console	Cause	Fix
postMessage … Invalid target origin 'null'	Page running at a null origin — a sandboxed iframe missing allow-same-origin, a file:// / data: / blob: page, or a CSP sandbox directive (see below)	Restore a real origin: add allow-same-origin to the iframe, or serve from the deployed https:// URL
AdError 303: No Ads VAST response	No demand matched — usually a null origin (see below) or an unregistered / missing-ads.txt domain	Fix the origin; use the registered domain; confirm ads.txt is live (Step 6)
No Prebid bid — GAM only	Normal — the header-bidding auction returned no bid and the request fell through to the ad server	None; informational
Ad never opens, no errors	SDK not loaded yet, or the trigger isn't a user gesture	Wait for ready; trigger from a click/tap
Player opens but the anchor is missing	injectionElementId div not in the DOM	Render the anchor div and keep it mounted
Duplicate <script> warnings in dev	React Strict Mode double-invokes effects	The hook already dedupes; ignore in dev
window.initializeAndOpenPlayer is not a function	Calling before the SDK finished loading	Gate calls behind the hook's ready flag

For the complete list of ad-error type strings (the ~38 VAST/IMA codes returned by error.getError().data), see the Local callback error codes reference.

When the origin is null

A null origin is the single most common cause of silent no-fill, and it is not limited to React Native — a plain React, Next.js, Vite, or CRA app hits the exact same failure whenever the browser strips the page's origin. When the SDK reports a null origin, the consent postMessage fails (Invalid target origin 'null') and the ad request returns AdError 303: No Ads, even though your domain, API key, and ads.txt are all correct.

Check whether any of these apply to the context the SDK is running in:

• Sandboxed iframe — the SDK (or your game) is inside an <iframe sandbox="…"> that does not include allow-same-origin. A sandboxed iframe reports its origin as null to everything inside it. Add allow-same-origin (keep allow-scripts as well): sandbox="allow-scripts allow-same-origin". If you control the embed, the simplest fix is to drop the sandbox attribute entirely.
• Non-https page — the page was opened as a file://, data:, or blob: URL (common when testing a build locally by double-clicking the HTML). Serve it from the deployed https:// URL instead.
• CSP sandbox directive — a Content-Security-Policy: sandbox … response header (without allow-same-origin) does the same thing as a sandboxed iframe. Remove the directive or add allow-same-origin to it.

To confirm what the browser sees, run console.log(window.origin) (or document.location.origin) on the page that hosts the SDK. If it prints "null" instead of your https:// domain, one of the above is the cause.

For React Native WebView specifically, the same rule plus the WebView setup is covered in Step 4.

Still stuck?

• Confirm the page's origin is a real https:// domain, not null — see When the origin is null. It is the cause of most "no ads" reports, on both web and mobile.
• Confirm your domain is registered (exact match) and ads.txt is live.
• Email support@applixir.com with the domain, your API key, and a console log — that is exactly what lets us diagnose fill issues fastest.