After upgrading from Hudson to Jenkins the only option offered on the "Manage Jenkins" page is to downgrade back to 1.395.1 despite your changelog showing many other newer versions/upgrades (1.420 being latest) that followed the 1.409.1 version. Attempts to go through the "Advanced" tab of the "Manage Plugins" option against "http://updates.jenkins-ci.org/update-center.json" do not show any updates are avialable.

Have researched to make sure the issue is not a missed configuration setting on my end, but can not get this functionality to work.

Have an older CI box where this issue is not happening and the link to upgrade is showing up. Added screenshot to show you the missing link.