You might want to take the cover off the unit and retrieve your CD. It
may have fallen from the carousel somehow. Just don't force anything.

These players usually won't open until the turntable is properly
aligned with the traverse unit (playing mechanism), and the traverse
unit has been lowered out of the way. If you're hearing rotation, the
unit is in the lower position already.

The sensing devices that determine the table position may not be
functioning. The most common cause is a defect in the "flexy" cable
from the drawer to the main PCB.

If the trouble is more involved than just an out-of-place CD, be kind
to your Onkyo and take it to a repair shop. It doesn't sound like a
real serious (expensive) problem.

Good Luck

Doug