Same problem here. Running Webex Productivity Tools 188.8.131.52 for Outlook integration. These process is preventing sleep of my Mac (Mac OS 10.14.6).
The command "pmset -g" shows the power settings. There it is mentioned "sleep prevented by Webex Productivity Tools". Also Acitivity Monitor in the Energy tab shows that.
As soon as I close Outlook, also the Webex process is closed and sleep works again.
Maybe an update will fix that issue?