Why does SharpCap say there are no updates when there is a newer version on the download page?

New versions of SharpCap are usually only added to the auto-update system after they have been available for download for several weeks. This approach allows time for any significant new bugs to be found by those who download and install manually, avoiding the possibility of a large number of people installing a buggy version via auto-update.

If you want the latest version then just download and install manually from the download page.