Every file in the folder is syncing but one

After not adding any files to my sync folder for about a year, I just added one. At first I thought the problem was a Google Drive sync issue, but then I copied all of the files into a Dropbox folder and synced that folder. Just like with Google Drive, every old file synced except of the new file. This has happened both with GDrive and Dropbox. I'm flummoxed.