I downloaded & installed Simple-Dropbox-Upload-Form, v 1.3.0.
I downloaded, installed Dropbox 1.2.49 and set up DBx account.
I went thru the 6-step installation for the Upload-Form, with what appeared to be confirmation that each step completed successfully.
I inserted the [simple-wp-dropbox] code on a page, but when I previewed the page, I rcvd the error msg in the Topic Title.
I marked the page to NOT show on the Menu, and published the page.
Same error message when display the page.
Don't see anyone else with this error, but with the minimal install/setup instructions, I must be doing something wrong. Could problem be with Dropbox.com? How can I check?