Quicken offers a coupon for 5GB free Dropbox storage for Quicken subscribers. However, upon submitting the code, Dropbox says my code has already been used. This seems to be a common issue as there are many similar posts in the Dropbox Community, but without resolution. Some say they chatted with Dropbox Support, but I don't find a channel for contacting Dropbox directly. I could really use the additional 5GB of Dropbox storage. How can I resolve this?