Google Calendar notifications, from my synced Microsoft 365 calendar, are inconsistent on iPhone.

This makes no sense. I selected my 365 calendar account within the Google Calendar settings as a calendar to sync/display in Google Calendar, and notifications are turned on. The calendar is syncing correctly, because when I open Google Calendar, I see all the 365 entries. Google Calendar is giving me notifications on all the entries that were in my 365 calendar as of a few days ago, but anything I add to the 365 calendar doesn't result in a Google Calendar notification. But meanwhile, the calendars are still syncing correctly. So, the Google Calendar is synced correctly and shows the new items, but isn't giving me notifications for them. Anyone have any ideas?