To fix the "Your connection to this site is not secure" issue in Microsoft Edge, several effective methods can be used:

1. Check the website's SSL certificate by clicking the padlock icon in the address bar to ensure the certificate is valid and not expired.
2. Enable TLS protocols (1.2 and 1.3) in Edge through Internet Properties > Advanced settings to allow secure connections.
3. Clear browsing data, including cookies and cached files, in Edge settings under Privacy.
4. Enable the Automatic HTTPS feature in Edge by navigating to edge://flags/#edge-automatic-https and selecting "Enabled," then restart the browser.
5. Temporarily disable antivirus or firewall software as they can sometimes block secure connections.
6. Update Microsoft Edge to the latest version to ensure compatibility with current security protocols.
7. Reset Microsoft Edge settings to default if other fixes do not work.

These steps address common causes such as outdated browser versions, misconfigured TLS/SSL settings, and interference from security software, helping restore secure website connections in Edge.