Our old Jenkins instance stopped working when it would not load older plugins at all and we could in NO WAY make it go back to a functioning state.  FINE.  We needed to update anyways.

New Jenkins instance in a fresh (blank) JENKINS-HOME. Fresh plugin downloads ALL around.

Tried the LTS version (2.361) and ran into this problem.  Updated to 2.377 to try and address it.  did NOT work.

We have (unfortunately) literally thousands of old jobs (which we keep for SCM purposes) which depend on the Join trigger.  This trigger HAS to work.  I have loaded up the custom join trigger build by Mr. White and that did NOT address the issue either.  Its not that the trigger does not work, it does not RUN.  Log attached from /var/log/jenkins.log.

I DO have the parameterized trigger installed and we require that plugin as well.

I can provide a sample job if requested, but honestly, a blank job shows the same behavior.

The Join Trigger item IS in the list of Post Build Triggers.

This is 100% reproducible.