How many ADT Sensors does the ADT Smartthing alarm support

I have been working on setting up my Alarm and automation over the last few days. Changing from a Smarthings link on my Shield. Took the plung on the ADT setup. I am seeing what looks like a limit imposed on the number of ADT based sensors. I am setting up perimeter protection so a sensor on each door and window. I have a total of 18 and i can’t seem to get above 15 ADT sensors. If i didn’t know any better i would say it is capped at 15. Is this true. Have others confirmed this.

Smartthings suppor just responded and stated the number should be 64 ADT Sensors. I tried again today and it worked. so not sure what caused the hiccup but they are connected now.


I had the same issue at 10 sensors. Retried later and it worked fine.