It sounds like you’re experiencing an issue with a third party application. We can't offer help with configuring/troubleshooting that unfortunately, as it's made by a third party.
Please reach out to the support organization for that app for help. If the developers of this app are having any trouble with the Dropbox API itself, they can reach out to Dropbox developer support directly with the relevant technical details.
For reference, as an end-user, you generally shouldn't have to interact with the developers site yourself. This is something the developer of the app should do.
