Error messages

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

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

ChatGPT shows this in place of a reply, sometimes in red, often with a code in brackets after it:

Unusual activity has been detected from your device. Try again later. (880a555898eb77a8-LHR)

The code changes every time. The letters after the dash differ too (people in the big forum thread about it posted LHR, MAD, AMS, FRA and ARN), so paste the whole line, code and all, if you contact Support.

What OpenAI says it means

OpenAI's troubleshooting page for ChatGPT errors files it under "Unusual Activity Detected" and says: "This message is shown when our systems detect traffic that may resemble automated or unusual behavior." So it's a guard against bots and abuse. It's also a different message from "Suspicious activity detected", the banner that says someone else may be using your account and tells you to secure it.

The first suspect on that page is the network. It asks you to turn off VPNs and proxies "that might route your traffic through flagged IPs", restart the browser or device, try a private window, and make sure you aren't sharing the account. If you don't use bots or automation, it says to contact Support.

If it only happens in the iPhone app

OpenAI has a section for exactly this line in its network recommendations article, headed "ChatGPT iOS error". As of October 1, 2026 the steps are, in order:

• Log out of the ChatGPT iOS app and log back in.
• Uninstall and reinstall the app.
• Disable your VPN.
• Update to the latest version from the App Store.

If it still fails, the article's advanced steps are to change the iPhone's DNS servers to 8.8.8.8 and 8.8.4.4 (Google's public DNS), then open Safari and go to https://register.appattest.apple.com/. That's an Apple address. If Safari shows an error there, such as "Safari can't open the page because the address is invalid", screenshot it. OpenAI wants that screenshot in your Support request, along with confirmation that you tried every step above and are on the latest app.

Forum reports fit the iPhone pattern. One person in September 2024 got it "whenever i want to use the ChatGPT app on iPhone though it works on everything else", and reinstalling didn't fix it. Another, on an iPhone 13 in April 2025, couldn't use the app at all.

When it comes and goes on the web

The longest thread on OpenAI's forum about this line started in May 2024 and reached 79 posts. Most people hit it while regenerating a reply or using a custom GPT, and several said a retry or two got through. The person who opened it wrote a week later that "it fixed automatically". No OpenAI staff member replied in that thread, so nobody from OpenAI tied that wave to a cause.

There's also a newer, wordier banner that people confuse with this one: "Unusual activity detected. You've sent a large number of messages in a short time, so we're doing a quick check to keep ChatGPT safe and reliable." That one is about message volume. A Pro user posted Support's reply in August 2025, which called it a short hold that clears on its own.

Older wording

Before this line, ChatGPT said "Our systems have detected unusual activity from your system. Please try again later." People were still posting that version in early 2025, with "coming from your system" in some reports. The help center's advice is the same for all of them: VPN off first, then a fresh session, then Support.