Can't mount SMB share

[TheOldPresbyope]

I recently got a new Synology NAS device (DS1019+) to replace my old Synology NAS (DS213j) and I've been having trouble mounting a shared folder over SMB. The logs keep showing "mount error(13): Permission denied".

• Mounting a shared folder from my old NAS works fine. I've tried making sure the new NAS has all the same SMB settings with no success so I'm baffled.
  
• I tried opening an SSH shell and manually mounting the folder from the new NAS and it seems to work fine. This does me no good, however, since the mount doesn't show up in the Moode GUI.
  

Any ideas what I could be doing wrong?

On my systems, mount error(13) is induced when I send a SMB server the wrong credentials (username/password). Just one might expect from mount's explanatory text message "Permission denied".