The owner's manual for the subject car says to "Press and hold the Set
(Tune) button until the numbers flash".

The Set (Tune) button does not seem to depress. I've tried every other
button (press and hold) but none makes the clock numbers flash. As far
as I can tell this is not related to the radio security code -- the
radio works and displays normally and the power hasn't been
disconnected.

I would appreciate any light shed.

Thanks!