Dropbox recently deprecated their original (v1) API, which is still used inside of Ensembles, and they have announced it will stop working in around a year from now. Where does this leave Ensembles?
For now, apps will continue to work fine, so there is no immediate rush. But within the next few months, we need to start taking steps. We will be moving the Dropbox backend in Ensembles to the v2 API, either using the REST API, or perhaps using an as yet unreleased Objective-C API. We expect to begin that work in August, and it should be ready a month or two after that.