Circle only records when it detects motion in its field of view. Once Circle records, you should see activity bubbles (recorded clips) on the right-hand side of the Circle app. You can scroll down to see older activity bubbles if you have any. 

The blue bubbles mean high activity level and the gray bubbles mean low activity level. If you don’t see any blue or gray activity bubbles, check that the Event Filter choice is set to “All Activity” (to access the Event Filter menu, tap the three bubbles on the top left of your Live View). Also, make sure Privacy Mode is not enabled, or Circle will not record any footage even if it detects motion.