There is currently a problem for those playing osu full screen. The banner shows your Online/Offline status, but does not show song info. This is related to a fix in the latest osu update:
[peppy] Don't set window title when running osu! fullscreen.I believe that givenameplz is working on a solution at the moment. For time being, those affected can try using borderless instead (which still displays song info through your signature).