Are you using something to change the mode of the hub? I use this to trigger events, not the presence sensor itself. Basically it will pass a direction to change the hub status. Trigger your alarm.com change from hub status not device presence. See the Nobody Home app screen grab attached.
You might want to also look into Life360 and IFTTT to accomplish what you want. The cell phone presence has been finicky and Life360 seems to manage presence well for people having issues with SmartThings presence.