Thanks for the answers !
I want to give some feedback in case anyone has a similar message from AC.
My flight was canceled on 07/28
I asked for a voucher on 07/28
I received my voucher (and 4 digit pin code) on 07/30
The voucher was loaded with the amount today on 08/02 and can now be used for new reservation.
So , it took 5 days.