If you see the "Connection not established" message, please make sure your phone and PC are connected to the same network (for example, to your home router). Then restart Stepl on PC and scan the QR code again.
If you still see the "Connection not established" message, try this: open Windows Firewall settings, Private Network, and turn off the Firewall, then restart Stepl. Or add Stepl to the Firewall exclusion list.
To make sure Stepl works when your phone screen is off, set 'No restrictions' and 'Do not optimize' in the 'App / Battery' settings. Only if that doesn't work then press the 'Stay awake' button that can help with some phone models. 🏃💪