Websites password synchronization issues between Mac and iPhone

I have recently updated my iPhone to iOS18, and when I update a password in Safari on my Mac (macOS Catalina 10.15.7), it doesn't update on iPhone.

On the other hand, if I update the password in the app Password on the iPhone, it is correctly updated also in Safari on Mac.

I have the same issue when I save a new password from a new website: when I save it from my iPhone, then it is also synchronized in Safari on Mac; when I save it from Safari on Mac, it doesn't synchronize in the app Password on the iPhone.