The photos taken by Samsung Galaxy are not immediately synced to Dropbox for some reason. It seems it takes several hours to sync them, although the phone is connected to Wifi and also syncing over a cellular network is allowed and there are only 1-2 photos to upload (the problem is not the size). It is very inconvenient... a year ago the same problem were solved when I opened Dropbox app on the phone (then immediatly the files were synced). But now it seems that simply opening the app does not help either...