you will have to wait to sell the tickets until the rescheduled date is known. At that time the event will be available on Stubhub to both buy and sell tickets and you will be able to list your tickets.
Elton has rescheduled his Toronto shows for
Feb 14 2022 (formerly 3/28/20
Feb 15 2022 (formerly 3/29/20)
Stubhub will be updating the dates on the site and you can then resell your tickets.
For other dates and venues - https://www.eltonjohn.com/stories/fybr-rescheduled-2022