check your connection, Sign in, activation, or connection errors | CS5.5 and later
if you're trying to update something,
pre cc updates: http://www.adobe.com/downloads/updates/
cc updates: http://prodesigntools.com/adobe-cc-updates-direct-links-windows.html
cc 2104 updates: http://prodesigntools.com/adobe-cc-2014-updates-links-windows.html