Group xxxx could not be found. Please confirm the existence of the group with a Confluence Administrator.
One good way to control permissions on wikis.mit.edu is to set up a group in Moira containing everyone who needs a particular set of permissions on a wiki space, and then give that group permissions on the Space Admin page.
However, sometimes a group will not appear in the group search and cannot be added.
The group must be a group (not just a mailing list) in Moira.
If no one in the group has ever logged into the wiki server, then the group will also not be found.