I've booked tickets for my parents on the following route:

CHC - SYD - BKK - DXB - VCE (and return) on Economy Flexi Plus

They have points which will Expire on Dec 31 (more than enough for a one way upgrade) so I'm trying to upgrade part of their trip with Miles to J.

The booking system is showing that most of the legs are unavailable to upgrade however it's giving me the option to be notified for DXB > CHC

Is it a case of it's too early for the upgrade option to be available or is it simply that those J seats have already been sold?

Futhermore, why isn't it giving me the option to be notified for the other legs?

Hope that makes sense. Thanks!