I used to rely on the Calendar app on my Samsung Galaxy. Then, something changed. Maybe it's that I upgraded the phone; maybe an update broke the calendar functionality. Either way, for some reason, alerts now no longer work.

I was supposed to be on a call today. It was scheduled a week in advance, so I used the Calendar app. The event was set up, and was configured to alert me 30 minutes before. The time zone was correct. The phone was on; sound was on; and the app was permitted to alert and show notifications.

There was no alert. I was not present on the call, and this may have cost my company business.

I remembered this happening once before, but at that time I figured I must have configured something incorrectly. This time, I double checked. An alert should have happened, and did not.

My wife uses a different Samsung Galaxy with the same app, and has also experienced alerts that don't occur.

I tried switching the Samsung Calendar app for the Google Calendar app. But the same thing occurred: I create an event, set up an alert, all settings appear to be fine, and... no alert when the time comes.

All other non-Calendar apps seem to have no issues ringing or displaying notifications.