Acrobat 9 (Standard or Pro) will no longer download updates automatically from version 9.0.0 at least that was my experience on 6/30/16. Acrobat 9 is no longer supported by Adobe. Luckily, I found this page:
The page explains that while the autodownload function no longer works, you can manually download the updates from here:
PC - ftp://ftp.adobe.com/pub/adobe/acrobat/win
Mac - ftp://ftp.adobe.com/pub/adobe/acrobat/mac
I found that when I got to about version 9.3.5, the autoupdate feature *did* work, but the autoupdate feature definitely did not work on version 9.0.0.