"You need to be logged in to view that page" alert for authenticated user
First off, checking access as user 1 or Administrator is not a test because no permission checks are done for user 1, and in most cases Administrators have all permissions.

Two, your permission is mixed case, change it to all lower case and clear the cache.

Three, in order to access anything under /admin, user will also need access administration pages permission as well - or whatever permission is assigned on that menu item (I think that’s the one).