Unless your .pls file is an audio file, which is unlikely, you generally cannot convert pls to ogg. This is due the fact that .pls are in most cases playlists and these do not contain any audio data that could be converted to actual audio file, such as Ogg Vorbis Audio.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.