If you try to log in to ChatGPT and see the preauth_cookie_device_check_failed error, or get blocked mid-chat with "Unusual activity has been detected from your device. Try again later.", you are not alone. When turning off VPN and clearing cookies does not help, the issue is more likely a temporary OpenAI-side outage than a problem with your personal settings. This post covers the symptoms, what the community is reporting, and what you can do right now.

Error Symptoms

1. At login: preauth_cookie_device_check_failed

On the ChatGPT website or app, tapping the login button stops before authentication completes, and developer tools or the error screen shows:

preauth_cookie_device_check_failed

This error means device, cookie, or session verification failed during the pre-auth stage. It can appear at the same time across browsers, mobile apps, and Google/Apple sign-in.

2. While chatting: Unusual activity detected

If you are already logged in or in the middle of a conversation and see the message below, your session has been blocked.

"Unusual activity has been detected from your device. Try again later."

This is OpenAI's security system flagging your device, network, or session pattern as suspicious.

Why Are So Many People Seeing This Suddenly?

As of July 2026, Reddit's r/OpenAI community has multiple threads reporting the same symptoms. When many users hit the same error at the same time on different devices and networks, it is more reasonable to suspect a ChatGPT authentication or security server issue than an individual account problem.

Reference: r/OpenAI – Anyone else having issues?

Common community reactions

"It's not just me" – users worldwide report login failures on the same day
"VPN off and cache cleared, still broken" – standard troubleshooting does not fix it
"Web works but the app doesn't" (or the reverse) – symptoms vary by platform
"Just wait it out" – past similar outages recovered after OpenAI deployed a fix
"Check status.openai.com" – look for Authentication-related incidents on the official status page first

If your experience matches that thread, waiting for OpenAI to fix it is the practical choice. Repeated reinstalls or re-signups are less useful than watching for an official recovery update.

Basic Steps You Can Try (Optional)

Even when the root cause is server-side, these steps are low-risk to try. Failing all of them is normal and further points to an OpenAI-side issue.

Check OpenAI Status for ChatGPT or Authentication incidents
Temporarily disable VPN, proxy, Private DNS, and ad-blocking extensions
Clear browser cookies and cache, then try logging in from a private/incognito window
Set your device date and time to automatic (helps prevent session token errors)
On mobile: clear app cache → update to the latest version → reinstall if needed
If the app fails, try chatgpt.com in a mobile browser

When Should You Contact OpenAI?

Consider opening a support request through the OpenAI Help Center if:

The same error persists for more than 48 hours
You have a paid (Plus/Team) subscription and access is completely blocked
The error screen shows a Request ID, Ray ID, or other tracking code (submit with screenshots)

Helpful details to include: account email, full error message (preauth_cookie_device_check_failed or the Unusual activity text), time and timezone, device/browser/OS, and whether you use a VPN.

Summary

ChatGPT login errors such as preauth_cookie_device_check_failed and "Unusual activity has been detected from your device" are tied to OpenAI's authentication and security systems. If you are not the only one affected and communities like Reddit are reporting the same issue at once, waiting for ChatGPT to fix it is the right call.

In the meantime, check status.openai.com and retry after a few hours or a day if it is not urgent. Most temporary outages clear up automatically after OpenAI ships a patch.

Related Links

ChatGPT Login Error: preauth_cookie_device_check_failed · Unusual Activity (2026)