If you're encountering a #400 Bad Request error when trying to access Vivint links, here's a step-by-step guide to troubleshoot and resolve the issue.

1. Check the URL: Ensure that the URL you are trying to access is typed correctly. Look for any typos, unnecessary characters, or spaces which can lead to a bad request.

2. Clear Browser Cache and Cookies: Outdated or corrupt cache and cookies can cause issues. Here's how to do it:
- Open your web browser.
- Go to Settings > Privacy and Security.
- Click on "Clear browsing data" and select "Cookies and other site data" and "Cached images and files."
- Click on "Clear data."

3. Disable Browser Extensions: Sometimes, installed extensions can interfere with your connection.
- Access your browser settings.
- Find the "Extensions" or "Add-ons" section.
- Disable any extensions temporarily and refresh the Vivint page to see if the issue persists.

4. Flush DNS Cache: Flushing your DNS can help resolve network-related issues.
- Press Win + R to open the Run dialog.
- Type cmd and press Enter to open the Command Prompt.
- Type ipconfig /flushdns and press Enter. You should see a message confirming that the DNS resolver cache has been cleared.

5. Check Internet Connection: Ensure that your internet connection is stable and working correctly. Try accessing other websites to confirm.

6. Restart Your Devices: Sometimes simply rebooting your computer and modem/router can fix unexpected errors. Turn off your device, unplug the modem/router for a minute, and then turn everything back on.

7. Try a Different Browser: Switch to an alternative web browser like Google Chrome, Mozilla Firefox, or Microsoft Edge to see if the issue is browser-specific.

8. Contact Vivint Support: If none of the above steps resolve your issue, it may be a server-side problem with Vivint. Contact their customer support for further assistance.

For additional details on fixing a 400 Bad Request error, you can refer to the following resources:

- Hostinger on fixing 400 Bad Request errors - [learn more]

- Cyberchimps' guidance on the 400 Bad Request error - [learn more]

- Lifewire's steps for troubleshooting the error - [learn more]

- BetterDocs on resolving 400 Bad Request errors - [learn more]

Following these steps should help you resolve the #400 Bad Request error and access Vivint links without issues.