iMac + USB Superdrive NOT compatible?

I have a 27"iMac whose internal Superdrive no longer writes DVDs or CDs. I tried cleaning ( Wet + Dry methods) with no success.

Instead of a costly repair or a possibly botched DIY fix, I had a cunning plan!

I bought an External USB Superdrive!

Assuming it would just Plug & Play, I am disappointed to find that it is completely invisible to my iMac!

I would have thought that a piece of Apple Hardware would be instantly recognised and kicked into life, but no.

Can anyone help?

Cheers.

Jim Hunter.