favorite generates "500 internal server error"

Using the mastofe user interface, I try to favorite a post that I made on my own (new) server. I get back a 500 Internal Server Error toast on the bottom left of the screen. Nothing obvious in the log files, and no favorite shows up in my favs list.

02:34:15.125 request_id=2lgv7a8ojevh8ceqto003uq3 [info] POST /api/v1/statuses/255/favourite
02:34:15.131 request_id=2lgv7a8ojevh8ceqto003uq3 [info] Sent 500 in 6ms

Is there somewhere else I should be looking for a traceback?