If they are .con files, most of them will say ‘songnamehere’.rb3_con and/or will simply look like a standard unidentified file on Windows systems. Those files MUST go into the right category in your HDD or they won’t work. Also, this issue can happen with Modio if you pull out the Thumbdrive if it hasn’t completely finished it’s current process.
Btw, are you using RB3Maker or the NEW LeFluffie for RB3?
You are about to leave Rhythm Gaming World and access the external songs DB. While no song or file sold for commercially available videogames is hosted there and only fan generated content is allowed, Rhythm Gaming World has no direct control over the database and no files are hosted here. Alright, we had to made you aware of this, now you can visit the database!