I just booked JL YVR-NRT-SGN for September a few days ago, and availability had been showing up.

In my experience, the availability matched with BA (and AA, but AA doesn't show that far ahead). So if you see it on BA, but not showing on CX, then it may be worth contacting them

I haven't looked into this, but CX has been having transfer issues from card issuers lately? They've been traditionally picky about name matches, and from Canadian card issuers, it's been taking a lot longer than other airlines.