iCloud Keychain not syncing to my Mac

Hello,

I've been using iCloud for many services such as Notes, Reminders, iCloud Drive and Keychain for a long time withh my Mac, iPhone and iPad.

A few weeks ago, I've noticed that new passwords have not been syncing to my Mac if I've registered somewhere on my iPhone.

I've disabled iCloud Keychain, restarted, re-enabled it.

I've waited for hours on Wifi, plugged in etc, no avail.

Then I've tried logging out of iCloud on my Mac completely and logging in back again. I've got a confirmation on my iPhone for 6-digit number, took a few minutes to re-enable it, entered my passwords etc. In a few minutes everything including my iCloud Drive files, Notes, Reminders were back on my Mac, but my keychain is still not here. It's again been hours and my iCloud Keychain on my Mac is completely empty in Keychain Access.

iCloud keychain is enabled on my iPhone and I've left both my Mac and iPhone plugged in, fully charged, connected to Wifi for hours, but I'm still not getting anything on my Mac.

How do I get my keychain back on my Mac (without resetting, of course)?

Also, I've heard that there is some sort of security code that can be added to iCloud Keychain. However, that option is not available anywhere on any of my devices. Would that create a difference?

Thanks,

Can.