You may need to change the command mode on the receiver and remote. Click here
to learn how to change your Sony receiver (and its remote) to AV1 (or AV2) Command Mode.
Search for AAP040 and follow the instructions for the STR-DN1000 receiver.
If you change the command mode on the receiver, you will also have to change it on the AAP040 remote if you want to continue using that remote also.
If this doesn't work then you might consider getting a learning remote.