We switched https to on last week and since we did, Jenkins is not posting Rocket.Chat Notifications for the specified events anymore.

Furthermore, both Test Connection buttons display "Success", the button in the Job sends out a notification as well.

What could cause the Plugin, to not send the specified notifications?

Some output from the jenkins.err.log file on our machine.

2019-08-30 12:08:30.625+0000 [id=60633] INFO j.p.r.RocketChatNotifier#perform: Invoking Completed...
2019-08-30 12:08:30.625+0000 [id=60633] INFO j.p.r.ActiveNotifier#completed: Build completed. Checking for rocket notifiers
2019-08-30 12:08:30.643+0000 [id=60633] INFO j.p.r.ActiveNotifier#completed: Could not send rocket message