I received these two comments from tickets I opened.
The STHM Send Text Message option won’t save any contacts I enter, but text messages from Automations and SmartApps work fine, and they responded.
I would like to inform you that we have recently noticed the issue, where some of the users are not receiving the text messages, This is the know issue on which our team is currently working. We do not have any expected ETA when the issue would get resolved. Once the issue is fixed you will receive an update.
On another ticket I have open they advised that there is this apparent restriction.
The total number of automation behavior should be less than 250. Each device/condition/action in automation counts as a behavior. For example, one automation that controls 10 devices has 10 behaviors