Issue:

DropBox has shut down the v1 API which is what we currently use in the DropBox connector. 

Resolution:

As a workaround use File / Open / DropBox and File / Save As / Dropbox.  These options still work because they does not use the connector, but instead uses the Dropbox desktop client's sync folder directly.

Connectors /-Dropbox; any Open or Save dialog no longer works.

Open from DMS - Dropbox or Save to DMS - Dropbox no longer works.

Reference:  https://blogs.dropbox.com/developers...v1-deprecated/