My Cloud not Syncing folder from USB Drive connected to Mac

My Cloud OS 3 Personal & Network Attached Storage My Cloud
1

I have a Mac and a USB drive connected to it. Folders that I have added to be synced from the MAC are syncing fine. The folders from the USB drive although added to the SYNC list is not being synced. I have tried rebooting, removing the folder and re adding but still not working. Any tips will be appreciated
Thanks