Media System Plus - not detecting OGG Vorbis files

[DragonQ]

I have Media System Plus in my 2014 Seat Leon and it doesn't recognise any of the OGG Vorbis files on my SD card. It finds the AAC and MP3 files though. The user manual specifically states:

– Digital specification of the audio.
-Rates of 160 kbit/s (recommended)
up to a maximum of 320 kbit/s and 48
kHz of sampling frequency.
– Audio files in MP3, WMA, OGGVorbis
and ACC format.

All of my files (including the AAC and MP3 files that work) are VBR encoded. Has anyone got OGG Vorbis working via SD card? Is there something I'm missing here?