---
title: "Troubleshooting SSL certificate upload issues"
canonical_url: "https://www.nutrient.io/guides/document-engine/knowledge-base/remote-url-certificates/"
md_url: "https://www.nutrient.io/guides/document-engine/knowledge-base/remote-url-certificates.md"
last_updated: "2026-05-14T21:57:26.840Z"
description: "Learn to resolve 'Unknown CA' SSL errors and ensure seamless document uploads from URLs with these best practices and troubleshooting tips."
---

# How to fix 'Unknown CA' SSL errors in document uploads

Question: What to do when I can't upload document from a URL because of the 'Unknown CA' error or other issues related to SSL certificates?

Answer:

In order to upload a document from a URL, Document Engine needs to make an HTTP request to fetch it from the given server. It's unable to complete this request due to invalid, expired, or malformed SSL certificates.

The most common issues related to the certificates are:

- certificate is expired

- certificates in a chain are not ordered correctly

If you encounter issues related to SSL certificates, we recommend checking your certificates with SSL Labs online tool: https://www.ssllabs.com/ssltest/. Also, you can read about best practices when it comes to deploying and managing SSL certificates in this guide: https://github.com/ssllabs/research/wiki/SSL-and-TLS-Deployment-Best-Practices.

---

## Related pages

- [Monitoring Document Engine](/guides/document-engine/knowledge-base/monitoring.md)
- [hash_mismatch error](/guides/document-engine/knowledge-base/hash-mismatch-error.md)
- [Remote document storage](/guides/document-engine/knowledge-base/remote-document-storage.md)
- [Signing service not available](/guides/document-engine/knowledge-base/signing-service-not-available.md)
- [How to convert an XLSM file to PDF using Document Engine](/guides/document-engine/knowledge-base/xlsm-to-pdf-conversion.md)
- [Fix PDF download issues with NGINX reverse proxy](/guides/document-engine/knowledge-base/unable-to-download-pdf-with-nginx-reverse-proxy.md)