The legacy configuration program allows you to lock/unlock the settings - there is a tick box on the Setup page. I suspect that the previous owner "locked" the settings.

Nick

Sources: Auralic Aries G1 & Re-plinthed Thorens TD-150/ISOkinetik Power Supply/Linn Ittok/AT33PTG/Trichord Dino
Speakers: DSP3100
Other: QNAP TS-451+ as a Plex and Roon Server, Samsung 4k TV-Plex Client