MyBook 6T won't backup completed video files

My WD MyBook 6TB drive just did a successful backup of my files to Dropbox, but it didn’t backup any completed video files. How can I get it to do that? I want to use Dropbox as a cloud backup of all my video work. I have plenty of room left in my DB account - only used 25GB out of 1 TB.
Thanks.

Hello there,

Where you using a backup software or manually copying files to the Dropbox account? Also try to see if you get any error message when trying this.

I was using the SmartWare software included with the drive, and there was
no error message. Everything else loaded fine, and the video files were
included in the folder I selected to backup.