I've looked everywhere and haven't seen anybody post anything similar to my situation, so here goes...

I have J ticket SFO - HKG after making booking I went into my bookings and changed my seat assignment, I look every few days to see if a seat opened up in the mini business class (rows 11 & 12) as this is a nice quite section. Nothing has been open but I keep checking. A few days ago the "update" seat assignment is no longer available on this first leg, all other legs it is still available to update. I am many days away so it's not that I'm too close to departure to change.

So my question is this.

I am 11,000 shy of hitting 0.50 million miles could this be blocked as I'll get op-up Mile Milestone upgrade, even before the Milestone hits?

I'm also several months away from 5 consecutive years anniversary of DM. Could this be another possible op-up prior to anniversary date?

I've never seen the website not allow seat changes.

Just curious if anybody else has had this and was it indeed an op-up planned a week in advance? Or am I just screwed with seat that was given at booking?

Thanks in advance for any insight!