Password 8 Safari Extension not working

I have been running 1Password v8 (Macintosh) since its release, currently at v8.7.1, running on an iMac with macOS Monterey 12.4 and Safari v15.5 (17613.2.7.1.8). (Actually, I have been a 1Password user since v3.0.)

But in the last 2 days, the 1Password for Safari extension is not running (not even showing it is available) - no 1Password icon in the browser window, no extension listed in the Safari: Preferences: Extensions pane, no 1Password icon or prompts when I am in a UserID or password field. (The 1password app works okay, and the menubar icon and QuickAccess work just fine.)

I have uninstalled 1Password.app and uninstalled 1Password for Safari.app and redownloaded them. I have the latest macOS and Safari versions installed.

When I launch 1Password for Safari, I get a little window telling me to Open Safari Preferences. When I open Safari Preferences: Extensions, it shows 3 other extensions (disabled) but does not list 1Password anywhere.

When I go into your Support page and click on the article "If 1Password isn’t working in your browser", it tells me that "1Password is not installed in your browser. Learn more."

Any ideas?

1Password Version: 8.7.1
Extension Version: 2.3.5
OS Version: 12.4
Browser:_ Safari 15.5