Hey, thanks for looking into this for me! Looking at your questions above, I realize I've been using the term 'autofill' incorrectly... I always have the auto-fill functionality disabled in the plugin preferences. What I've actually been talking about is using the plugin button up on the toolbar to pick a matching entry and then fill the login details on the webpage.
When it's working after a disabe/re-enable, the "Show Matching Logins" will have one or more entries in it and the plugin button on the toolbar will have the number of matching entries in the little red overlay.
When it stops working, I still get the red overlay on the toolbar button, but "Show Matching Logins" doesn't show up in the menu when I click the button.
Hope that explains my usage better.
I don't have direct access to the server where PasswordState is running in IIS, but I can say that we're definitely not using Microsoft Monitoring Agent or SCOM.