Just purchased a brand new 2018 Passat loaded with every option possible.
It came with the new 9 inch infotainment audio system and somehow it will not play any Whatsapp audio or video audio. I was told that whatsapp audio now plays on OPUS format.
Anyone have any hint on updating its Codec or any other trick so it plays these audios?
The interesting thing is that it will play on my other 2 cars with very old stereos systems...
Depends what the audio system is running and what format the files are in. It isn't clear to me what you are actually doing (plugging in downloaded files on a USB stick?), but if older stereos support the files in question without converting them, they're probably MP3 or similar which should be supported.
Create some different files, MP3, AAC, OGG, Opus etc en try that out or check the manual, which lists all the supported filetypes.
For a firmware update you should contact your dealer. Usually they know exactly what to do. Sometimes you can do it yourself via the unofficial way, like I did with my Peugeot system (via USB), but because it is a new car I would check with the car dealer.
AFAIUnderstand, there is a range of VW/Skoda/Audi entertainment systems with different properties. Probably you should ask at VW/Skoda user forum.