I am the owner of a space in Confluence, and an administrator of Confluence.
The space has been in place for a number of years, and no recent changes have been made.
Now I get an error 'You've stumbled on restricted content' when I try to access the space page. It suggests I ask the owner for permission, but I repeat - I am the owner.
This page has a restriction that means only I and one other user can edit the page. The other user gets the same message.
Other pages within the space are still visible, even if they have restrictions on them.