Wait until 72 hours before the date of travel. 72 hours is a common threshold now, but by late April it could be longer or shorter.
So with no way to reach Chase/Expedia, I called Delta to ask about my reservation, especially since it was still showing as active even though the flight to Madrid no longer actually exists. I was trying to get Delta to refund the value of the tickets to Chase/Expedia where, presumably, I would eventuallly be able to get that ticket value refunded to me in the Chase points I paid for it. The Delta agent did acknowledge that my flights did not exist, and cancelled the reservation, but said that Delta was NOT refunding for cancelled flights right now. She said I could use the value of the tickets to book another Delta flight by the end of the year.
I know times are hard, but this does not seem right to me. Cancelled flights should be refunded. I have no idea whether I will want to book a flight on Delta for this ticket value by the end of the year. Does Delta have the legal right to do this?