Playing music files from NAS

I have now installed a NAS with my .flac files and connected everything to ALLO BOSS2. The only problem I have is that I can only play the music starting from the first file of each folder and than change track only by going one by one clicking on the “next” arrow. I can’t play another track except starting from the first and I can only proceed with the arrow to go to the next. The back arrow is also not working. Please help. Many Thanks.