Normally CCleaner tells me a new version is available to download. I see v3.21 has been available for eight days yet no reminder when I start the program (daily). I do have "automatically check for updates to CCleaner" ticked.
Strange. I can't comment on it possibly being an error, since I follow the update schedule and update day-of manually.
Well of course it offered it today. I know other programs sometimes take a while before updates are offered through the internal updater (although that's not exactly what CCleaner's is).
It may wait a week before offering it.