the Kenwood has two wires: Blue/White for an amplifier turn-on, and Blue for power antenna. The Blue/White wire is used to turn on the factory amp. Hopefully the wire harness you bought has that connection, otherwise you need a different adapter.
GM uses a Pink wire for factory amp turn-on, and a Pink wire for power antenna.
Verify the factory Pink wire is connected to the Kenwood Blue/White wire, you may also have a Pink wire connected to the Kenwood Blue wire. Or there may just be one Pink wire - in which case you connect it to the Blue/White wire.
If you mix those up, you will have sound with the Radio only.