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I cannot see the Admins page, why?
Short answer: This page is reserved for the account's Owners. Without that role the tab does not appear, and the direct address shows: “Admin management is restricted to the account's owners.”
The other roles are not enough
Shops, Money pot and Promotions each open their own page, not this one. Only Owner carries the right to manage other people's access.
Asking for the role
A current owner of the account can grant it from this very page, by ticking Owner on your profile. The change takes effect straight away, with no need to sign in again.