I found a reply to a similar question that linked this to the need to delete
ANONYMOUS from the permissions list. Doing this has worked. Merci for any
replies.

"Tricio" wrote:

Occasionally, I will see a WHITE BAR with BLACK STRIPES when checking other
calendars. I know this occurs when trying to access calendars across
firewalls, but that is not the case with these displays. These are calendars
of people within my orgnaization and firewall.

I assumed this is because they have set their permissions to NONE with
Folder not visible. But, I have experimented with this with some of my
colleagues, and have not been able to replicate this. Is this display the
result of some other setting(s)?

Merci.