It is not possible to run Alarm.com scenes using Google Home. There has been no change in this for a long time, unfortunately. I am not familiar with all the walls in this case. I believe there were policy issues last I checked.
As an alternative, Alarm.com scenes are supported in Amazon Alexa skills if it is required through a voice control.
Another option may be Siri voice shortcuts:
Otherwise Alarm.com scenes can also be set up as widgets on your phone home screen to trigger with one tap.