Snapshot Pro - Sorry! That page doesn't seem to exist.

I have a site running WordPress 4.6 that I am trying to use the snapshot plugin with.

I have it set to do a daily database backup, and this works fine. I am also trying to set it to do a weekly full backup including all files. They are scheduled to go to a Dropbox folder, but I have the same problem with the local server as well.

When I run the backup, it goes through all the database tables and gets to the file, and it then shows me what looks like an embedded page from my site that says "Sorry! That page doesn't seem to exist." and fails to go any further.

Thanks in advance.
Chris