Yes, I suspect that you did not open and close the front door.
When you arm to Away Mode, in order to complete arming, you must exit the house, ie go out of the front door and close it. This allows the system to arm to away mode
Away Mode means that everyone is Away from the house. you do not arm to Away Mode and stay in the house. Otherwise you should arm to Night Mode
Are you saying that you do not have a alarm contact on the entry door that can act as an Entry Door Zone Type?
It is advisable to always have an entry door Zone, so that it can end the exit delay and arm after the door has closed. The doors and windows on the ground floor should have contacts as these are the primary alarm protection. It is not good to rely on the PIRs or motion detectors as the main alarm detection because these only work when the intruder is inside the house. Furthermore, motion detectors may have to be disabled when people are in the house to prevent alarms so it may prevent you from arming to Night Mode.
If you really cannot fix the alarm contact on the entry door then you should set the Away Arming Method in Security > Arming and Disarming to After Exit Delay
The options for Away Arming Method are
Final Door (Preferred)
After Exit Delay (NOT preferred)
Exit Terminator - need to press the doorbell to arm the system
If you select Exit Delay then there is no need to exit the house when you arm to away. But it is not the proper way to do it at all