At the end of last year, Dropbox announced a new interface (called an “API”) for coders (like the people who create UpdraftPlus) to use. Following this successful launch, in June of this year, they announced a deprecation plan for the former API.
The long-and-short is this: the previous way of accessing Dropbox will stop working on 28th of June 2017, and you will need to update to a compatible version of UpdraftPlus before 28th of June 2017 comes, if you want to continuing sending backups to Dropbox. That gives you plenty of time to update – just don’t forget!
Which versions are compatible, you ask? This will be our next release onwards, scheduled for the end of this month (October 2016, in case you Googled and found this some time later). This should mean version 1.12.24 (free version) or 2.12.24 (paid versions) or later. I repeat – these aren’t yet released. But they’re coming soon!