I’ve also had some issues the past few days with SmartAlarm not fully arming (It would give me the “Arming in 30 seconds” message, but never actually arm). As of now, things appear to be working right, but that doesn’t mean much if they don’t stay that way.
This looks like it’s related to the various SmartThings scheduling issues, including RunIn() jobs not being scheduled at all:
Hopefully ST Support can get things fixed up, so we’ll stop seeing issues, and get back to normal.