I have also had this problem with the classic pebble. I did let misfit know that I was getting an error message. I believe they are trying to work on the issues I described below.
In addition to the the syncing issues, I was unable to log into my misfit account (via pebble) and connect the Pebble to the misfit app. I factory reset my pebble and did was unable to sync and the misfit app wouldn't recognize the Classic Pebble.