Unable to display certain pptx files - spinning wheel in the Meeting room

We are unable to display multiple pptx files in Adobe Connect. This is happening if we try to directly share the content from the Desktop or even if it was already uploaded into the Shared Content. It is not happening with all the decks, only some - but there is nothing to indicate what the problem is. 

If we go to the Web portal and try to play the slides, it does not progress from the 'Adobe Presenter' screen. 

Has anyone come accross a similar situation? Any tips or workarounds?

Thanks in advance!