I am using the stock Reminders application. I had Fantastical years ago but haven't used it recently. A reminder that I created yesterday (to have a look at Saturn and Mars this morning) generated an alert, but older reminders still don't.Question to OP: are you using stock Reminders, or some 3rd party app?
Can't remember now (been a while) what sequence of events and which tools (might have been a version of Fantastical) caused this, but had to whip up a Shortcut to go through all my Reminders and automatically re-add the alerts (for all Reminders with no Alarms copy Due Date to Alarm).




Can anyone chime in about alarms? I've never had them fail me. I've used those in the past for important reminders.
Thanks mate. I'll give this a try. What Mac OS are you on?I seem to have fixed this, perhaps temporarily, by re-entering all my reminders and deleting the old ones. I only had about a dozen, so it wasn't a big deal. For now, Reminders are again reliable.
Trying out Due. It is $7/yr but not a subscription - which I appreciate. Plus others in my family can try it out. Thanks for the suggestion.Reminders wasn’t working for me either. I gave up on iOS reminders as well. I moved to Due. Love that I can continue to snooze a reminder until I act upon it.