Really confused about synching contacts and reminders
2023 M2 Mac Mini
2020 M1 MacBook Air
2020 iPhone SE
All devices have latest OS updates.
When I add or edit or delete a contact on the Mini, it synchs with my phone. But when I add or edit or delete a contact on my phone, it doesn't appear on the Mini's contacts.
My reminders, which I only add, delete, or edit on the Mini, do not synch with the phone or the MacBook.
I have researched this and can find no similar situation. My head is spinning with all the different configurations among the various devices. Most important, though, is that when I make a change in my phone's contacts, I want it to update the Mini's.
Any advice appreciated.
Mac mini (M2, 2023)