This is a replacement as the one I purchased on 6 December was great until the battery had to be changed and then did similar things to this one (the replacement) I tapped it this morning and it showed yesterdays steps, I tried to sync it and then is went to 0 so I went for a walk ,approx. 8000 steps and it didn't register anything.

Tools & Hardware - Others - Fitbit - Zip Wireless Activity Tracker, Charcoal