Alarm duration after activation

Just wondering if anyone can help? We have just purchased the keypad and motion sensor so was testing it out in away mode. We had set it to away mode and then walked in as if we was an intruder. The alarm on base unit sounded when the motion sensor picked me up aswell as the camera but the alarm only sounded once and stopped. Isn’t the alarm supposed to carry on until I turn it off manually?
I have checked the settings in the app and the auto switch off for the alarm is turned off so it should carry on sounding until I turn it off if I’m correctly thinking.

Can anyone advise?