The "auto-pause" feature is managed by the Lumo Run App on your phone and can be managed from the "Settings" of your Lumo Run App.
When you have the "auto-pause" feature "ON", when the phone stops moving (based on input from the phone's accelerometer) your Run is paused. This is to "pause" the time and pace calculations when you stop running (e.g. if you are stopping to recover or resting for a while or at a red light, etc), and it will resume when you begin running or walking. It is intentionally designed to "not" pause the time and pace calculations when walking because we appreciate that many of our runners like to have their walk-time included in their overall distance and pace calculations.
Please note that the sensor only calculates the core metrics on your "running form" (Cadence, Braking, Rotation, Bounce and Drop) while running. If you do not want your walking time included in your distance and pace, simply manually pause your Run in the Lumo Run App when you start walking and resume your Run when you begin to run again. Also see "How would Lumo Run track my run if I use a run-walk method?” for more information.