I am using NC18.04.
I don’t understand why the address book cannot be synced on iOS.
It has two-step verification, and the application password has already been issued.
However, when I set it up, the message “Cannot connect via SSL. Would you like to set up an account without SSL?” is displayed.
Even if you press the Continue button, the message “The CardDAV account could not be confirmed.” will be displayed.
The calendar could be synced in the same way without any problems.