A lot of my guest users are missing their view of shareable boards in their individual accounts. I have checked to make sure my guests are still subscribed to the boards which they are. Please look in to this asap.
Can you ask your guests to log in again to check? We were seeing an error for guests earlier today but it has since been resolved.
If you’re still having trouble, can you shoot us an email at email@example.com with a screenshot of what your guests are seeing?