Schedule trigger doesn't actually trigger

I have a bunch of build configurations, but I can't seem to get our nightly builds to actually run. The schedule trigger is this:

    Date/Time: Cron command: 0 10 4 * * 2-7 *  (Server Time Zone - GMT Europe/London)
    Next scheduled time: 08 Aug 17 04:10 UTC+1 (Server Time Zone)
    Will trigger builds in branches matched by filter:
    +:refs/heads/*
    Clean all files in checkout directory before build.

The build itself however never actually runs, just accumulates pending changes (it's over a week old so it had plenty of chances to run at night). If I tell TeamCity to build a particular branch manually, then that works as expected. I'm on 2017.1.2 (build 46812).

I have set TeamCity to log everything with debug-all, but I don't see anything in the logs around 4:10, just this repeating over and over:

Build Triggers Monitor 1 start: 0 msec
Build Triggers Monitor 1 done: 0 msec
Flush Queue 1 start: 0 msec
Flush Queue 1 done: 0 msec
Flush Queue 1 start: 0 msec
Flush Queue 1 done: 0 msec