Address auto-fill not working on Gmail

A couple days ago email address auto-fill stopped working on Gmail. The suggested addresses still appear, but clicking on one of them won't cause it to fill the address field.

I figured this was one of the many little glitches that would resolve by rebooting the Chromebook, but it has persisted.

Is there some kind of auto-fill switch that I inadvertently turned off somehow? (Seems unlikely since I'd imagine that turning it off would stop the autofill suggestions from popping up.)

If not, is anyone else having this trouble?

I'm using Minimalist for Gmail, although I've had no other issues with this extension in the month that I've used it.