Radiation: What do big dogs do? No key to the cage, no dialogue.

The dog locked himself in a cage, so he had the key, so you couldn't get it.

You should have had a tape before, which was given to you by Neya, who talked to you after entering the door. Playing tapes outside the kennel can trigger a conversation with the dog.

Turn off all the radio simulations next to the dog. Don't turn them off.

As for the method of playing the tape, I repeat:

Open PP kid, modulate the data (the last of the three buttons below), then select "record", click on the recorded data you got before, and then close PP kid until it finishes playing.