as an administrator why cant i see all spaces?

[Chris Psaltos]

I am the sole administrator for my cloud version of confluence. For some reason I am the only person who cannot see some spaces.

Why is that?

[Nic Brough -Adaptavist-]

Because system-admin rights are for doing system administration.  Not "I can see/do everything" - that's a terrible permissions model, and thankfully one Atlassian stay away from. 

As a system admin, I don't want to be able to see everything in a 5000 space, million page Confluence, I want to see the spaces that are relevant to me.

For the "invisible" spaces, check the permissions - you can still do that as an admin, even when you're not able to see the content.