Which patch under bulletin APSB17-17 are you trying to apply? Some of them are downloadable and some are not. Only the latest Adobe updates are downloadable through the software, so you're probably looking at a slightly outdated patch.
For patches that are not downloadable, this doc covers the process of manually supplying them so you can still deploy them if you'd like:
It's worth noting that all of the standard patches under APSB17-17 have been superseded by APSB17-21. The debugger patches are the only ones under APSB17-17 that are still downloadable, but they have been superseded as well.