The A6000 was supported as long ago as LR 5.4 - see Cameras supported by Camera Raw . It's not a compressed format, is it? I don't know much about Sony, but I wonder if that's the problem.
As an experiment, put the ARW file in a folder all by itself, then see if you can import it.
Thanks for the advice. I'll try downloading the latest update and see whether that makes a difference. Much appreciated.
Thanks for the reply John. I'll try that (putting it into a separate folder) as well as updating to the latest version of LR6.
Pretty sure the file's not compressed though: it's a 25MB file with an ARW suffix (pretty much the same as the DNG and CR2 files I'm used to processing from my Canon).
Rather oddly, my son says he can open the ARW files directly using an older version of Lightroom (LR5).
I guess the file size indicates it might not be an unsupported compressed variant.
The thinking behind a separate folder is that Lightroom might be thinking the file is a duplicate or even a sidecar. Are you absolutely sure the photo isn't already in Lr? If so, that would be another way to make Lr fail to import it now.
Nice work! I updated LR6 to the latest version and updated Camera Raw but neither appeared to make much difference when it came to "seeing" the ARW file. Once I had updated the software I still couldn't "see" the ARW file in the folder alongside the DNG and CR2 files.
So I created a new folder and navigated to that folder from scratch. LR happily imported the ARW file from there.
Not sure what was going on (and not sure I got the sidecar reference) but it was like LR was stuck at only seeing DNG and CR2 files in the original folder and needed a completely new path to see additional files not associated with those suffixes. Very odd.
Anyway, problem solved. Much appreciated.