If something's wrong

On Windows and Linux, right-click x4u's icon by the clock to open it again. If there's no icon, start x4u again; it says so if something else is in the way.

x4u is working through new videos, at low priority. The bar at the top of the page says what it's doing, and it stops when it's done.

Look in Review: it may be waiting for you to pick a match, or listed under Not found, where you can search StashDB for it.

Check both are on the same network, that Settings → Other devices is on, and that your computer's firewall lets x4u in.

It isn't in its folder any more. If you moved or renamed it inside your library folders, x4u finds it on its next look, with its details and history. An unplugged drive's videos are kept until it's back.