One thing that might be missing in the document is that you should execute "importprivkey" before downloading the whole blockchain (if you need to download it).
If not: you need to restart your wallet with the -rescan option. This may take a while.
As far as I remember importprivkey takes a third boolean argument which defaults to true. This third arguments tells the wallet to do a rescan (takes also a while).

Probably you need to call importprivkey "some label" true

Or how already said: start the wallet with a -rescan argument.

Kindly note that you won't see your funds until the blockchain is fully downloaded. (Depends on the coin but that's certainly the case for CENT) CENT has around 900k blocks and it can take about 48 hours until the blockchain is fully downloaded.

Edit: In case that you're still downloading the blockchain and we're talking about CENT: you don't need to do anything right now. Just wait



Thank you very much.