I don’t recall any successful use of Digital Life sensors with an Alarm.com compatible panel. I’m a little confused by that but they may have updated their equipment or made other changes.
Historically, I believe Digital Life sensors used Zigbee RF, not 433mhz. But, admittedly I don’t have a lot of experience with them.
I just looked at some documentation and it seems to imply that AT&T has a 433 Mhz repeater that is used for sensor signal boosting, so they do use 433.
It would be easier to confirm compatibility with sensor model numbers. What are the model numbers of those sensors you have? Can you post a photo of the sensor labels?