> For the complete documentation index, see [llms.txt](https://doc.thordata.com/doc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.thordata.com/doc/faq/product-problem/general-questions/what-should-i-do-if-the-proxy-cannot-connect.md).

# What should I do if the proxy cannot connect?

Please check the following in order:

1. **Protocol** — rotating residential and mobile proxies support HTTP/HTTPS only.
2. **State or city filters** — select the country only. Filtering too finely can leave too few available IPs, which returns a 502 (Resource\_203) or an SSL error.
3. **Port matching the product** — 9999 for residential and mobile, 6666 for static ISP.
4. **Credentials** — characters are often lost when copying. Regenerate the proxy string and try again.
5. **Your local network** — confirm that your region is within our service scope. If you are unsure, contact support first.
6. **Entry point** — the `as` / `pr` / `va` host segments are interchangeable; some variation between entry points is normal.

You can also test from the command line: `curl -x "http://<user>:<pass>@<xxxx>.eu.thordata.net:9999" "http://ipinfo.thordata.com"`

If it still fails, send us your registration email and a full screenshot of the error. Range-level issues are usually resolved within 1–5 hours. A 502 with Resource\_203 from the target site means that domain is restricted by an upstream provider.