Here, There, Everywhere...
Yesterday (May 12th) we experienced an email service outage from approximately 12:30pm to 8:00pm PST. If you invited anyone to share a folder during this time, they likely did not receive the invitation email. We don't yet have support for re-sending an invitation, so for now the best option is to remove any impacted users and then re-invite them.
To re-invite a user:
Thank you for your understanding and for participating in the Live Mesh Tech Preview to help us make a better product.