I think you got a PA-RISC based Unix box. Probably, it does not support normal PC Monitor. It will have a console port on which you can plug in a null modem cable and a dumb serial terminal. You can try to get a terminal emulation software on a PC and connect PC serial port to console port of the server. Then see it displays anything. You might have to set various combination of serial port like baud rate, bits, parity etc.. You can ask the seller to provide a console also with the server.
I have worked with HPUX server and they are fantastic workhorse. But PA-RISC and HPUX is already dead!! What you plan to do with it now? I could not understand HP's strategy to kill its own beautiful product. Come on, it is not an Inkjet printer which is born every six months!