When viewing the incidents list we have always right clicked and opened in a new tab.
Since upgrading to 16.1 we are no longer able to do this.
This functionality was intentionally removed to prevent issues with multiple tabs having the same session ID and creating problems in write functions to the database.
Due to popular request, this functionality is due to be brought back in one of the next releases.
In the meantime you can use the work around of holding down the left ctrl key on Windows, or the Command key on Mac while clicking the incident and it will open in a new tab.