If you like to check all your subscriptions for any update at once, you can click the 'Check Subscriptions' button located in the toolbar of the 'Subscriptions' tab, as depicted above.
Alternative Way 1 :
In the 'Latest' segment of the Home Tab, there is a sidebox at the right titled 'One-Click Away Functions'. In that box, you will see a link named 'Check my subscriptions' to start to check.
Alternative Way 2 :
Ziepod provides keyboard shortcuts for frequently used actions and there is one shortcut dedicated for this checking action. There is no default key combination for this action. If you like to set it, check out the corresponding related help topic.