Not all types of content sharing allow remote control; you usually need to share your entire desktop to give someone full control, it could be that the participant sharing content has joined from a web browser, instead of the Webex Application.  You ...

It’s alerting you that a message wasn’t sent in that space.  To resolve:  Sign out of the Webex app on your phone and delete the application and re-download it.  Before you log back in via the mobile app I would reset Webex from a pc/laptop then log ...