I'll be trying this later this month.Flying DEN-IST-BKK and BKK-IST-DEN. I had upgraded my return married segments 2 weeks ago successfully through the app and also used miles to upgrade DEN-IST segment on the outbound, BUT TK cancelled my first outbound flight. They offered to rebook me in Biz on the outbound 2 days (!) earlier, which was a nice touch, but I declined. Unfortunately, the only way to rebook me onto a more convenient outbound was to cancel the entire ticket, forfeiting all upgrades. I rebooked the proper outbound and same return, but the complimentary upgrade was no longer available, even though there were at least 4 J seats still available on both legs that I ahd already been upgraded on. So, I keep checking but will need to wait to 24 hours before to try to get a last minute upgrade.

Can both married segments be upgraded with the complimentary upgrade 24 hours out if at least a seat remains?

Thanks!