Calendar notification banners not showing on new iMac after migration

Bought a new iMac M4 2024 and used migration assistant to transfer files from my older macbook pro (2013 using Big Sur ver. 11.7.10.) The iMac is up to date.

The only issue I'm having is my calendar notification banners don't show up on my screen at the specified time. It worked fine on my old macbook. I tried turning off iCloud and manually putting events back in. I entered a test event on the calendar to notify me later that night twice and it worked, but all my regular event alerts still don't show up on my screen. All notifications in system settings and calendar settings are turned on and I don't use Focus. I'm stumped now. Any ideas?

[Re-Titled by Moderator]

Original Title: calendar alerts not working