Last night I checked both the volume control under the hatch and the background volume. They were both in the highest position.
Thank you for Mike's e-mail. I sent him an e-mail yesterday. He came back to me with a few troubleshooting ideas but unfortunately none have lead to any success. I'm currently patiently waiting for another response. I feel that this reefer should be considered a lemon (3 fix attempts and still not working).