You said that you sent email to developers, do you mean the Send to Committers checkbox?
From plugin description
Send to Committers - Check this checkbox to send the email to anyone
who checked in code for the last build. The plugin will generate an
email address based on the committer's id and an appended "default
email suffix" from Jenkins's global configuration page. For instance,
if a change was committed by someone with an id "first.last", and the
default email suffix is "@somewhere.com", then an email will be sent
to "first.last@somewhere.com"
Just installed the latest plugin 2.34 (needed to update jenkins as well) and noticed that there was no committers anymore but developers was there instead. Unfortunately, the help for the triggers was broken. So there are only guesses possible.
Check if the way to generate the email address is correct for your scenario and if you have setup the default email suffix.