Client Error On X | App “Attestation Denied” Fix

If you’re seeing “Client Error: App Attestation Denied” on X (formerly Twitter), it usually means the app failed a security verification check.

This often happens due to app integrity issues, device modifications, or network interference.

Since there was a major global outage on February 16, 2026, many users are still seeing lingering session errors. If you are experiencing this today, February 19, here is how to resolve the most common “Client Error” types.

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1. Most Common: App “Attestation Denied”

This is a specific client error on mobile where the app fails to verify that your device is “secure” or “official.”

• The Fix: 1. Check for an App Store/Play Store update. X frequently pushes security patches that break older versions.

  2. If updated, uninstall and reinstall the app. This clears the “Attestation” cache which simple log-outs don’t fix.

  3. Ensure your device isn’t in “Developer Mode” or “Rooted,” as X’s new security layers often block these.

2. Website “Client Error” (Login/Username Change)

If you see a generic “Client Error” when trying to log in or change your username on a browser:

• The Cause: This usually happens when your browser’s cookies and the server’s session token are out of sync (common after the recent outage).

• The Fix: * Open X in an Incognito/Private window. If it works there, you need to clear your site data.

  • To clear specific data: Go to your browser settings → Privacy → Cookies → Search for x.com and twitter.com → Delete all.

  • Avoid “spamming” the save button; this can trigger a 429 rate-limit error, locking you out for 24 hours.

Also Read : Is Zelle Down Right Now

3. Developer / API Error (4xx Codes)

If you are building an app or using a third-party tool and see a “Client Error,” it usually maps to these HTTP codes:

Code	Meaning	Common Fix
400	Bad Request	Check for typos in your JSON body or URL parameters.
401	Unauthorized	Your API Key or Bearer Token is invalid or expired.
403	Forbidden	You are trying to access a feature (like DMs) not included in your current API tier (Free vs. Pro).
429	Too Many Requests	You’ve hit your rate limit. Wait 15 minutes before retrying.

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Current System Status

While X’s “Developer Status” page often shows green lights, real-time reports on Downdetector show that some users in India and the US are still seeing “Something went wrong” messages during peak hours. If your internet is fine and you’ve cleared your cache, the issue is likely on X’s backend.