After upgrading yesterday, triggering stopped working today. There is some evidence that triggering did work for a time, but not conclusive.

I tried restarting Jenkins, then Gerrit. Nothing helped.

Saw logs of

Jul 18, 2018 5:07:57 PM com.sonymobile.tools.gerrit.gerritevents.GerritHandler checkQueueSize
WARNING: The Gerrit incoming events queue contains 28095 items! Something might be stuck, or your system can't process the commands fast enough. Try to increase the number of receiving worker threads. Current thread-pool size: 30 

(similar to JENKINS-52636), but the whole setup felt more like JENKINS-53738.

What finally helped was downgrading to 2.28.0 of the plugin. Then triggering started again. I never tried re-saving a job; we have a few too many of those that I want to do that for all of them.