probably how you're uploading it/syntax. dunno without seeing more of the stack trace.
One-X Attendant phone book from CM I used to list station in ASA, right click export as CSV and use that file to feed in to One-X Attendant
Did it work before?
If you try uploading a single entry, does that work? Maybe some station has a character in the name that is legal to CM but not to the app?