Incomplete folder on your HDD or within LW's library?

If you're using LW 4, go to LW's library & click on Incomplete Files. Now highlight a file & click Resume. The file should reappear in the download window. Download % might show as 0% but once LW finds sources, the download % should pick up from where it originally left off If you're not seeing download progress, start a new search for the file & that might kickstart the download.

If you're using LW 5, the incomplete folder doesn't show in My Library & there's no resume function. Downloads should automatically appear at the bottom of the page & either resume or show as 'stalled' - depending on if sources are found. If a download appears stalled, start a new search for the file... that might get things moving. But don't cancel the original download - this will remove the file completely from your HDD.