It mostly works fine, I've converted about ten playlists over the past few days and they all worked perfectly, but there's a particular playlist that comes up blank. I've noticed a few things:
I can convert from the text list to Spotify, and from that resulting Spotify playlist to Deezer. 95% of the songs are recognised but the resulting Deezer playlist is blank.
If I convert from the same text list directly to Deezer it only recognises about 15% of the tracks, but the playlist is still blank.
I suspected it might be unique characters (ö) so I removed the relevant songs, but it still outputs a blank Deezer list from Spotify.
I'm happy to share the Spotify playlist so someone else can test too. I donated about a week ago, if that helps. Love the app, thanks for the hard work.