This app is currently disabled.

Was the old employee a member of a Dropbox Business team? If so, I recommend having a team admin from the Business team opening a ticket with Dropbox developer support ticket here (while signed in to their admin account) if you haven't already done so. If they're an admin on the team with the (disabled) app owner, they would be authorized to more information, such as the account history and the app information for the disable member/app, which should be more helpful, or possibly recover the original app.

Otherwise, we'll be happy to help you get set up with a new app on your own account. Can you elaborate on what functionality you need to use on the API so I can offer some guidance on that? For instance, what Dropbox API methods does your code call (other than 'users/get_current_account' as seen in the output you shared)?