Privileges to select on a view - Issue
You need to grant select on the tables in schema A to the user B WITH GRANT OPTION.

From the documentation:


  To grant SELECT on a view to another user, either you must own all of
  the objects underlying the view or you must have been granted the
  SELECT object privilege WITH GRANT OPTION on all of those underlying
  objects. This is true even if the grantee already has SELECT
  privileges on those underlying objects.