We're getting an error with our Dropbox/Salesforce integration in a roundabout way. When we are trying to assign an Account in LeanData, we're seeing a "CANNOT_INSERT_UDPATE_ACTIVATE_ENTITY" error. "Dropbox_for_SF.DropboxClient.UserNotConnectedException" is also in the error. Screenshot attached. I cannot see a way to contact support, possibly because we are on the free integration. 
I'm not even really sure where to begin to troubleshoot! Has anyone else ever seen this?