There is a bug where discogs lookup fails even though songs are in the discogs database. That is if the artist or title has punctuation symbols in it.
example - Hi-Gloss - I'm Totally Yours will fail
but Hi-Gloss - Im Totally Yours will not fail
note the apostrophe on i'm
strangely this isnt always the case for example human league don't you want me works. it maybe to do with the song title being an album track rather than a release.
hope this helps...