Some server models and some client terminals are not ideally compatible with regard to special key combinations. For instance, on some HP servers, such as the HP DL380G4 (BIOS P51) server, the Alt-F2 key combination required to toggle to the login screen does not work for all terminal clients. Some terminal clients provide alternate key mappings, so it is worth checking the documentation of your selected terminal client to determine whether an alternative mapping is available.

If you are using the Windows PuTTY SSH client, then you can press Alt-rightARROW and Alt-leftARROW to toggle the login screen, instead of the printed Alt-F2.