First of all, it is the BigBlueButton server and not the plugin.
Second, I just had the same issue in one of my BBB servers for development a few days ago. Restarting did not work, so what I did was to run bbb-install.sh again.
The thing is that bbb-install.sh comes with a bunch of other checks to verify your configuration files. In your case I would try that first.
If that post your question to the bigbluebutton-setup google group. There are hundreds of System administrators there. They may have run into that issue too.
The thing is that me, personally, I am not working directly in BigBlueButton development at the moment. Mostly integrations and infrastructure, so I am not up to date with the updates that are done every week.