Looks like they're operating, but on different equipment under different fight numbers.
AA9601 operated in place of AA737 on Sunday, AA9602 operated in place of AA737 on Monday, and AA9608 will operate in place of AA737 on Tuesday.
I would guess this is due to an aircraft downgrade from 787-9 to 787-8.
Cancelling the original flight number in this circumstance allows passengers to rebook on any available alternative, that might be more convenient for them, at no charge.