Firstly, please make sure that you have connected the proper Dropbox account. You can verify this by disconnecting dropbox in the Zencastr dashboard, then go to dropbox.com and ensure that you are signed to the right account. Afterwards, return to the dashboard and reconnect your cloud drive.
If you are still having this issue then it may be due to having Tracking blockers installed. These can block the requests to dropbox. Please consider making an exception in your blocking software for zencastr.com.