Update - We are continuing to investigate this issue.
Jun 27, 11:13 BST

Investigating - Users of Firefox 67.0.1 on Windows based machines after starting slides in the Media Hub may have to contract and re-expand the pod for the presentation view to display. We are looking at a fix for this issue to ensure the presentation area automatically displays to presenters as expected. Presenters should use the Chrome browser if they are having any concerns.
Jun 27, 10:46 BST