SK AAR

I you already rebooked once following the cancellation, you will not be allowed to (invol) rebook again - unless there has been a cancellation or schedule change subsequent to the rebooking.

Anyway, even a voluntary rebooking should be possible without change fee, however, the fare will be recalculated, i.e. depend on the booking class available for your (new) flights. You may not like the add. fare to be paid in order to rebook but give it a try.