I had some emails like that, when I looked at their forums there were loads of people complaining about it. Seems to be some kind of bug in their back end. Eventually gave up on Dropbox when their Windows client turned into some horrible bloated upselling rubbish. Besides, I'd eked my free storage up to 13GB by referrals and what-not and doing their stupid Quest nonsense one year, and I already had twice that on OneDrive for no extra effort.