The rain sensor works like an on/off switch. When it activates, it will show up in "Device Updates". While its activated, the system will not water. Once it deactivates, it will again post in Device Updates, and the system will go back to figuring out which zones/when to water based on how you've set it up.
Double check to make sure you have it turned on to the Rachio. I just set my daughters Rachio system up, and I had a little trouble with getting the rain sensor turned on. I used the web app to Device settings to turn it on, thought it looked like I turned it on, but it really didn't. Finally went to the phone app and was able to turn it on there.