The last 500 microposts will be indicated - this may take some time. To see all microposts, the whole systems needs to be reindicated, which causes a downtime of Confluence.
During the first installation of the 2.x version, all existing microposts will be migrated to belong to default topics. This migration process may take quite some time. Please refer to the administration guide for more information.
Also the macro "microblog" doesn't exist anymore. All its features are included in the macro "Microblog timeline".