Dropbox didn't take all photos

[Tintype_18]

Been pondering this topic for a while but need to get some help. I listed twelve photos with a brief caption in an email. Then I downloaded the twelve photos to Dropbox. It took seven but wouldn't download the remaining five. Never had this happen before. Do I need to reduce them in some way? Asking this as I have opportunities for more writing and photography. A mentor said the less work for an editor, the better he/she will like you. BTW, one publication uses WeTransfer. Anyone familiar with it? Many thanks for reading and your replies.

[Tronhard]

You are most welcome.  I hope the information allows you to control your file management more easily.