How to Fix ChatGPT 4.0 Error “Unusual Activity Has Been Detected From Your Device. Try Again Later.”

Many PC, iPhone , Android phones users are reporting issue with the ChatGPT that they have recently reported a frustrating error message:

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

The issue often appears while performing simple tasks, causing the chat window to freeze and rejecting even normal English prompts. This error has become increasingly common, even for paid users, and the official support responses have not been very helpful.

This article explains what this error means, why it may occur, and the solutions that users themselves claim have worked.

What Does “Unusual Activity Has Been Detected” Mean?

The error typically shows up after ChatGPT 4.0 freezes or becomes unresponsive, followed by a rejection message such as:

“Unusual activity has been detected from your device. Try again later. (Error Code xxxxx)”

According to user reports, this may happen even when:

No complex or high-risk prompts are used
The user is simply asking normal informational questions
There is no VPN active
The device and browser have been used for months without issues

Some users noted that the error appears even on their first message of the day, despite being paid subscribers.

Common Situations When the Error Appears

Based on user discussions, the error occurred during:

Regular chat usage
Technical conversations (e.g., 3D printing parameters)
Reloading existing conversations
Browsing long-term project chats
Moments after uploading a file or typing a simple query

In some extreme cases, users reported entire chat threads disappearing after the error—resulting in the loss of hours of notes, calculations, references, and important work.

How do I fix “Unusual activity has been detected from your device. Try again later. (9878bea57d29585b-SIN)”

1. Overloaded or Corrupted Local ChatGPT Cache

Several users discovered that specific chat threads or local application data caused the issue.

Deleting recent conversations or clearing the app folder fixed it for them.

2. False Security Trigger

ChatGPT may misinterpret certain messages as suspicious, especially those involving:

Weapons
Modifications to devices
Legal vs. illegal discussions

Even innocent questions related to YouTube videos triggered the error for some users.

3. Mobile App Bugs

iPhone users experienced the issue strongly on the app, even without VPNs or network issues.

4. Account Glitch or Sync Problem

Logging out and back in resolved the issue for many people, suggesting a temporary authentication or sync failure.

Fixes That Real Users Confirmed Worked

1. Log Out and Log Back In

Many users say this single step solved the issue instantly.

Steps:

Log out of ChatGPT
Close the app or browser
Log back in

This alone fixed the issue for iPhone and desktop users.

2. Full App Reset (Mac Users)

One user listed the following steps that successfully resolved the error:

Sign out
Force quit the ChatGPT app
Delete the folder:
~/Library/Application Support/ChatGPT/
Uninstall the ChatGPT app
Reinstall
Sign in again

This method fixed the error consistently.

3. Delete Recent Conversations

A user found that:

The latest 1–2 conversations were corrupted
Deleting only those resolved the entire issue

This is helpful if you don’t want to delete everything.

4. Check Memory Usage and Free Space

Users who had 100% full ChatGPT memory storage reported that freeing memory helped restore normal functionality.

After removing old memories and starting a new chat, the errors disappeared.

5. Avoid VPN or Proxy (If Used)

While many users experiencing this issue were not using VPNs, some reports online suggest VPNs may occasionally trigger security checks.

If you’re using any:

Disable temporarily
Refresh ChatGPT

6. Use a New Chat Thread

For some, simply opening a fresh chat resolved the problem.

Old chats might be glitched, especially long-running project threads.

What If Nothing Works?

Some users reported that the error persists for days. In this case, try:

A different browser
A different device
Switching between Wi-Fi and mobile hotspot
Resetting browser cache

If you are a paid user, contacting OpenAI support is always an option, although several users have mentioned receiving limited assistance.

Conclusion

The “Unusual activity has been detected from your device” error is becoming increasingly common for ChatGPT 4.0 users. While OpenAI has not provided an official explanation, user reports suggest it often results from:

Corrupted local cache
Faulty chat threads
Memory issues
App glitches
False positive security triggers

Fortunately, most users were able to fix it by logging out, clearing data, or reinstalling the app.

If you are facing this error frequently, try the solutions above—especially logging out and back in or clearing the ChatGPT application folder.