Repeated Automator workflow fails to run in Calendar I'm on Mac High Sierra and I've set up multiple daily repeated schedules (around 10 workflows) to run Automator workflow and the first few days it ran fine, but after a week the alarm just stops working. 
The schedule doesn't even show up in notification center anymore.

Does anyone know how to diagnose/fix this issue?

Update

Everything works fine if I open up Automator and run it manually, just that calendar alarm doesn't trigger Automator workflow anymore.
Is your calendar in iCloud? I'm struggling to do the same thing. Automator calendar workflows need to be saved 'on my mac' but in my experience they get automatically shoved to iCloud, which does not support App Alerts. Try removing your Calendar iCloud syncing and then create your Automator calendar workflow.