Amazon Cloud Sync not working bidirectionally

I am running a NAS RN204 with firmware version 6.10.1.  I have it set to back up a specific folder (photos) to my Amazon Cloud drive.  This is set to back every 5 minutes and does so into the directory ReadyNAS_nas204.

Files and directories inside the NAS under photo get properly backed up to the Amazon cloud drive.  Even though I have the NAS set to sync bidirectionally, nothing I add or change on the Amazon cloud gets pushed back to the NAS.

Am I doing something wrong or expecting the cloud sync to work differently than designed?

Thanks in advance for any help.