Cannot Sign In to the App

Loading spinner spins indefinitely

Fixed in version 4.1.27: previously, if the server was unreachable within 20s, the spinner would keep spinning. Now it displays an explicit timeout error. Update the app (tray icon → Check for updates) — if your build is very old, reinstall from the website.

Connection error displayed

The app cannot reach api.php. Common root causes:

• Corporate proxy: the app does not use Windows system proxies yet — proxy environments may block traffic.
• Router firewall blocking outbound port 443 HTTPS traffic to our server.
• IP temporarily blocked by server fail2ban protection following multiple failed attempts.
• DNS resolution failure: cannot resolve www.dynamicdnspro.com.

App → Help → Diagnostics diagnoses this automatically. Or in PowerShell: Test-NetConnection www.dynamicdnspro.com -Port 443.

Correct credentials but sign-in rejected

Verify that you can sign in to the web portal with the exact same credentials. If the portal also fails, check password or account activation state. If portal works but app fails, update or reinstall the agent.