ChatGPT Not Working on a Work Network: Fixes

When ChatGPT works on a phone but not on the office network, compare the two paths before you change anything. The fix is usually a named allow rule or a proxy exception, not guesswork.

Symptoms

• chatgpt.com loads but the page is blank, stuck on a loading state or says "network error".
• Messages send, but responses never stream in, or stop halfway.
• Sign-in bounces between pages and ends in an error.
• Text chat works, but file upload, voice or image generation fails.
• Everything works on a phone with Wi-Fi off, on home broadband, or when the VPN is disconnected.
• It broke on a specific date for everyone, often after a firewall, filtering or VPN change.

The last two lines are the important ones. If the problem follows the office network, the office network is the cause.

Likely causes, most common first

1. Web filtering blocks part of the domain set. ChatGPT does not live on one hostname. Chat, static assets, authentication, file content and API calls use several OpenAI domains. A filter that allows chatgpt.com and blocks the rest gives you a page that loads and then fails.
2. A category block. Many filters classify AI tools as a category. If the business chose to block "generative AI" as a category, that is the policy working. Someone needs to decide whether ChatGPT is approved, then make a narrow exception.
3. WebSocket or streaming blocked. Responses stream. A proxy that does not pass WebSocket upgrades or long-lived connections will show a message that never arrives.
4. TLS inspection. A gateway that decrypts and re-encrypts traffic can break the Cloudflare bot checks OpenAI uses, or fail on certificate pinning in the desktop app. The symptom is a challenge page that never completes, or an app that refuses to connect.
5. DNS filtering. A DNS-based filter on the router or the endpoint returns a block page or nothing for one of the required domains.
6. VPN routing. Full-tunnel VPN sends traffic through a head office filter that has a different policy from the branch. Split tunnel sends some domains one way and some the other.
7. Platform incident. Rare compared to the above, but check first because it is the fastest to rule out.

Step-by-step fix

1. Check the OpenAI status page. If there is an incident, wait.
2. On the affected machine, open a private browsing window and try chatgpt.com. If it works there, the problem is an extension or cached site data. Clear site data for the domain and retest.
3. Turn off the VPN and try again. If it works, the VPN policy is the cause.
4. Connect the same laptop to a phone hotspot. If it works, the office network or DNS filter is the cause.
5. Open the browser developer tools, Network tab, and reload. Note which requests fail and to which hostnames. Failed requests to an OpenAI domain that is not chatgpt.com tell IT exactly what to allow.
6. Try the desktop app if you use it. If the app fails and the browser works, TLS inspection is the likely reason.
7. Send IT the failing hostnames, the time, the device and whether it was VPN or office Wi-Fi.

What IT should check

• Compare your allow list with OpenAI's current network recommendations page, which lists the domains ChatGPT needs on the web and in the apps. Allow the full set, not the front door.
• In the proxy or secure web gateway log, filter by the user and time. A category block, a WebSocket denial or an inspection failure will be there.
• If you use Microsoft Defender for Endpoint web content filtering, check the category assigned to the OpenAI domains and the device group the policy applies to. Our note on web content filtering in Defender for Business shows where those decisions live.
• If you run TLS inspection, add a narrow bypass for the OpenAI domains once the business has approved the tool. Record the bypass and its owner.
• Check the DNS filter separately from the web filter. They are often two products with two policies.
• For VPN users, confirm whether the tunnel policy differs from the office policy and align them.
• Make one change, retest with the reporting user, then close the ticket. Do not add a wildcard for everything with "openai" in the name to make the noise stop.

A network change to allow an AI tool is also an approval decision. If nobody has decided that staff may use ChatGPT for work, the block may be the right state and the conversation belongs with the owner. Our AI rollout diagnostic is a quick way to find out where the business stands.

When to escalate to OpenAI

Contact OpenAI support when ChatGPT fails on a clean network, in a private window, with no VPN, with the status page clear. Include the exact error, the timestamp, the browser and version, and any request IDs shown in the error. For Team and Enterprise, raise it from the admin account.

Do not raise a case for a failure that only occurs on your network. OpenAI cannot see or change your firewall. The domain list on their network page is what your IT provider needs, and the log entry from your gateway is what proves the fix.

Source basis

• OpenAI status page
• Microsoft: web content filtering in Defender for Endpoint
• Cloudflare: Gateway HTTP policies
• NCSC: network architectures guidance