Updating
How Silkwave Video keeps itself current.
Silkwave Video ships outside the Mac App Store and updates itself. When a newer version exists you are offered it, and it installs in place - nothing to download by hand.
To check yourself, choose Silkwave Video ▸ Check for Updates… from the menu bar.
After a Failed Import
When YouTube changes how it serves video, importing breaks until an update ships. Silkwave Video checks for one immediately when an import fails, rather than waiting for its next scheduled check - so if you are offered an update after a failure, accept it and retry the link. See Importing Videos.
Reinstalling
Download the current .dmg and drag the app to Applications, replacing the existing copy. Your library, transcripts, summaries, and speaker profiles are stored separately and are not affected.