The 500-level error is specific to bug below. This bug is not yet available externally but will be within 24-48 hours. This is actively being investigated and I'd recommend opening up a Cisco TAC case for tracking.   https://bst.cloudapps.cisco.com/b...

When you say that you cannot make the video any larger, are you referring to the self-view of the Webex Meetings client? 

To reiterate/clarify, the capacity table in the Video Mesh deployment guide refers to per-participant calls not meetings. 

Dana,   This is a feature that has been asked for but isn't yet currently in the product. Right now it is in development but there are no committed timelines for when it will be released.