Jenkins not indicating that there are updates for plugins

[John Lussmyer]

We are running Jenkins 1.616, and I've recently noticed that we no longer receive notifications that there are new versions of plugins.
When I go to Manage Jenkins, Manage Plugins, the Updates tab is always empty.
I've manually checked, and there are multiple plugins that have new versions available.

How can I get the update checking to work again?

[Daniel Beck]

Without specific examples, it's difficult to answer, but try upgrading Jenkins -- 1.616 is old enough by now (more than 2 years) that many plugins may need a newer core version.