A warning appears on launch and the app won't open

When you open a downloaded app, the OS may show a warning because it can't verify the publisher. After confirming that your copy of echo came from the official distribution source, launch it from the OS settings if needed.

If you see "“gnosis-echo” cannot be opened because the developer cannot be verified," press Done to close it.
Open System Settings → Privacy & Security and press Open Anyway near the bottom.
Open echo again and press Open on the confirmation screen. From then on, it launches normally.

If you see "Windows protected your PC," press More info.
Press the Run anyway button that appears. From then on, it launches normally.

If Run anyway doesn't appear on a company PC, your administrator has blocked unsigned apps. Contact your company's administrator.