It is a known issue that HP warranty scanning does not currently work. HP recently added CAPTCHA protection to its warranty pages, which makes it impossible for automated procedures to read the pages. We are researching other HP pages we could potentially use to retrieve the warranty info, but cannot give a release date for a fix. Development has found that different pages (e.g. the page you see when clicking the serial) provide different (or no) warranty results, so we may not be able to fix this issue at all.
The only way to track HP warranties for now is to manually add the warranty information by hitting the Edit Asset button on your asset pages or clicking the Assets link at the top of the web console and hitting the Editing Mode button on the left.
Warranty scanning of Dell, Fujitsu, IBM, Lenovo and Toshiba machines still works and can be enabled under Configuration/Scanning Setup/Server Options. You can rescan warranties by hitting the Rescan All Asset Warranties Now button on the same page.