RW2 files not supported.

The Panasonic Lumix GX-9 is not supported in Sierra, Apple only updates its RAW database on the current OS which is High Sierra.

Digital camera RAW formats supported by iOS 10 and macOS Sierra - Apple Support

Digital camera RAW formats supported by iOS 11 and macOS High Sierra - Apple Support

So you are on High Sierra but posting in the Sierra forum, ok. Have you had a look at the links I posted particularly the one for High Sierra you will find that the Panasonic GX-9 is supported. I have successfully opened RAW files from that camera. What version of High Sierra are you on, this may be relevant as the RAW processor database in HS is updated with successive OS updates.

Download macOS High Sierra 10.13.6 Combo Update

Bigsi999 wrote:

I A previous reply advised converting using Adobe products, surely Apple can do better than that?

Since the camera was released in March of this year Panasonic apparently hasn't provided Apple with the information/data to incorporate it into the next system update/upgrade. As soon as they do and an update is released that model will be supported. So get after Panasonic to get their act together.

The camera is supported in High Sierra, see the link above.

In order to use the files in Sierra the OP can use Adobes DNG converter, or another RAW processing app.

Perhaps the Panasonics own software can be used in Sierra.

Not really since Apple has basically given up on their support of photography.