Reboot it
After the last Fire OS update, the Kindle Fire I keep on a stand in my office as the designated digital assistant device stopped answering when I'd say the trigger word. It would acknowledge it heard the trigger word, giving me the little blue line across the bottom of the screen and making a noise, but it wouldn't do anything. Checked settings, nothing helped, and I just let it sit for a week or so as I stewed. Today I finally decided I'd had enough and I reset it back to the factory defaults and reconnected it. That seems to have finally done the trick, and it's back to working as it should - better, actually, as it now recognizes that I live in Hyattsville and not in Southwest DC (the previous address), so it gives me the right weather forecast when prompted. I know it's good digital stewardship to go in and clean stuff up every now and again, but what a pain.