Hey @TonyTonyTony, welcome to our Community!
Let's jump right into this!
Is it possible that you accessed a new Dropbox account, and not your old one? If you check your events page, what do you see there?
You also mentioned that your account got downgraded, is that correct? Is it possible that you were adding content using your Dropbox folder, but the account didn't have enough space to sync the changes?
Keep me posted!