Gnutella or Torrent files? If torrent files re-open the torrent files you originally downloaded from the sites.

For Gnutella files .. best technique is to manually re-search the files as you did originally before you downloaded them. Then 10 mins later right-click the search tab & choose Find More Results.

BTW the Fix Stalled, etc. tools have limited abilities. They do occasionally work. It's my guess they simply seek the previous IP addresses they were downloading from. If those are not online or changed (dynamic ip's), then they won't succeed. May also be limited due to the search horizon .. the previous host being further away in gnutella ultrapeer links distance (like power or phone lines .. further power/phone poles away.) Searching for new hosts of the file is the way to go.

In both cases, once the files actually start downloading again their previous download history % will show.