Vault2 cannot see FLAC files on my NAS, nor can I drag them across from the NAS to the Vault 2

First I should declare that I am in my first 24 hours of BlueOS experience having just acquired a Vault2 so I am a total newbie. Not sure what is happening but I have many FLACs ripped to my Synology NAS using EAC and all permissions are correct. I have mounted the shared drive using the BlueOS App on my iPad but cannot access the files to play them. 

Secondly when browsing in Windows File Explorer, I can see both devices but I cannot drag and drop the same FLAC files in to the Vaults Music Folder. 

Both NAS and Vault are hard wired to the router.

Is there a basic incompatibility with the files? Any thoughts and suggestions?

Solved: For the benefits of others in a similar situation. Make sure to point the share to the folder containing the rips, not just the drive. E.g., my original share was "\\NASname\music", But I have different sub folders for MP3s, FLACs and HD files. So my required share is "\\NASname\music\Filetype". After that all folders indexed perfectly :)