Running on a Raspberry Pi 400

Lately my home has been dumb and unassisted at random times, and the HA app can't connect to my HA rpi server. Ditto when I go to homeassistant:8123 in a browser. I'm trying to see what's causing this, but the logs in app only show since last restart. Tried plugging my Pi into a monitor and getting something from the command line but not sure how to do the equivalent of a Linux tail or whatever. Searching was surprisingly unhelpful. Any advice?

Thanks much!