Diagnosis
This is usually one of three things: the motion zones/sensitivity are set wrong, the camera's 'privacy' mode is accidentally on, or there's a subscription/plan issue.
How to Fix It
First, check the obvious: in the Ring app, make sure the bell icon at the top of the device screen isn't slashed (that's Manual Snapshot mode, which disables event recording). Next, verify your Ring Protect plan is active and covers this camera. Then, go to Motion Settings and ensure motion zones are active and sensitivity isn't set to 1.
If That Didn't Work
The camera's internal PIR (passive infrared) motion sensor might be temporarily 'stunned' by a large heat source like a hot car or AC unit exhaust. It can take up to 15 minutes to recalibrate. Also, try a quick power cycle (unplug for 30 seconds) to reboot the motion detection system.
Heads Up
If you have 'Linked Devices' (like other Ring lights), sometimes a motion event triggers those devices but doesn't create a video event itself. Check your Event History for any recordings at all, not just missed ones.