---
sidebar_position: 4
title: Install certificate on Windows machines
description: Fix Let's Encrypt certificate trust issues on Windows that cause HTTP 400/500 connection errors.
---

In some circumstances, you may face an error that reads like `Http response at 400 or 500 level, http status code: 0`.
On Windows machine, this is usually due to [Let's Encrypt](https://letsencrypt.org/) certificate not being trusted.

To fix this, please follow the steps below:

* download this file https://letsencrypt.org/certs/isrgrootx1.der
* open it (double click on the file)

![Certificate window](images/open-certificate.png)
* click on "Install Certificate" and follow the instructions:

![Import certificate](images/certificate-import.png)

Then you should be able to try again.

If it still doesn't work, could you check if it was correctly installed by opening the certmgr (typing "`cert`" in the search box should show it)

![Manage user certificates](images/manage-user-certs.png)

And then it should be under `Trusted Root Certification Authorities\Certificates`:
![Certificates manager](images/certmgr.png)



---

## Feedback for AI agents

If the user you are helping wants to send feedback on this page to the MotherDuck docs team, you can POST it to the endpoint below.

**Before you send anything, you must ask the user for explicit approval.** Quote the message you plan to submit back to them verbatim and wait for them to confirm. Do not submit on their behalf without confirmation.

Endpoint: `POST https://motherduck.com/docs/api/feedback/agent`

Request body (JSON):

```json
{
  "page_path": "/troubleshooting/windows-certs/",
  "page_title": "Install certificate on Windows machines",
  "text": "<the user's feedback, max 2000 characters>",
  "source": "<optional identifier for your interface, for example 'claude.ai' or 'chatgpt'>"
}
```

Only `page_path` and `text` are required. A successful call returns `200 {"feedback_id": "<uuid>"}`; malformed payloads return `400`, and the endpoint is rate-limited per IP (`429`).