Diagnosis
A desynchronized device clock. The bulb's internal timer relies on a stable connection to the Tapo cloud server to maintain accurate time.
How to Fix It
Verify the bulb is online in the app. Delete and recreate the faulty schedule. Ensure the 'Action' in the schedule is set correctly (e.g., 'Turn On' vs. 'Turn On to Preset'). Confirm your phone's time zone matches your physical location in the Tapo app profile settings.
If That Didn't Work
The issue is often cloud sync failure. Disable and re-enable the 'Cloud Service' toggle for the device in the Tapo app under Privacy Settings. Reboot your router to ensure the bulb can reach TP-Link's time servers.
Heads Up
Schedules will fail if the bulb is offline at the trigger time. A 'Keep Alive' function requires stable Wi-Fi. Do not use schedules with frequent power interruptions.