Perhaps the Century is in A.OPT 0, where it does not respond to IR commands. To resolve this:
Turn the Century to standby/off.
On the Beo4, press the POWER (Red Dot) button and LIST together. Then press LIST until OPTION is shown, press GO (centre button), and then press LIST to show A.OPT. Then press 1. The power light on the device may blink to show that it has been accepted.
They are various threads in the old forum 12-22 and one in the current one you’re reading now about the Century and the IR. None of the solution provide help mine to respond to the remote and I believe so far my IR PCB is dead. Maybe that’s your case too. Unfortunately it seems to be various models of IR board that make it difficult to find a solution.