can't add new contact
On MacBook Pro macOS Big Sur Version 11.0.1, I suddenly cannot add a new contact in "Contacts." I click the plus sign to begin adding a new contact, start typing in the information, but within several seconds suddenly the whole new contact abruptly vanishes, and I'm back in the basic view of all Contacts. There is no trace of the new contact I was trying to add, not even the few characters I was able to type. This happens whether or not I try actually entering information - even if I just sit there and wait several seconds, the new contact abruptly vanishes.
I thought "maybe too many contacts?" so deleted several. Same result.
Tried Quitting all other open apps. Same result.
Tried quitting and restarting Contacts. Same result.
Tried restarting the whole computer. Same result.
Workaround for the time being: add new contact on my iPhone, then (after a bit) it appears in my computer's Contacts, and I can edit it.
But I really want to be able to add new contacts on my computer.
Anybody know what the cause and cure might be?
Thank you.
MacBook Pro 15″, macOS 11.0