I'm using the latest builds:
Been a (very happy!) 1Password user for quite a few years now without a problem like this one.
About an hour ago (before I updated to 670007), auto-filling browser forms simply stopped working. My keybind is Cmd-Shift-\, which means that when it stops working, Safari does its fancy auto-zoom thing. Clicking the toolbar button directly had no effect (no menu, no error, no anything). I've had this happen before, and usually it means that 1Password Mini has gotten out of sync, or the browser extension needs updating. I did the following steps, in order:
~/Library/Safari/Extensions) and reinstall. This forced a reauthorization with 1Password Mini (as expected). The results here were… interesting. A new private browsing window was able to auto-fill, but the main window was not. Nothing happened, in fact. Selecting the toolbar button showed the menu, and it detected the appropriate logins and allowed me to click, but nothing happened.
I'm not entirely sure how to proceed. Hence, this post.
1Password Version: 6.7
Extension Version: 4.6.4
OS Version: 10.12.4
Sync Type: Dropbox