"No items to show" when trying to fill a saved login in Safari

Dave, the vault containing this login is enabled, and has always been. If I use "Open & Fill" from the macOS app, it works fine. As I mentioned in my original post, it's only when I navigate manually to the login page, then click on the 1P logo in the credentials window, that I see "No Items to Show". After that, I can go to the 1P extension in Safari, open the login and it will autofill. But the Safari extension no longer recognizes it for autofill as it did for years prior to this latest version of the extension.