Summary 


Version 2.2.xx and above of cloud drive mapper requires the end user to have edit permissions on the SharePoint site that is being mapped. However it is possible to achieve using read permissions with the modifications detailed below.



Solution


Under > Site Permissions   >  Permission Levels > modify the permissions on read  -  Ensure that enumerate files and folders in a Web site using SharePoint Designer and Web DAV interfaces is ticked 





If the above hasn't resolved the issue then the user can be added to the site visitors group under the permissions on the site and then retested.