The product connects to the head unit normally, but when a rear screen is connected via HDMI, the rear screen shows a black screen.

1. Reset the product and check for and install product updates.

2. Check the head unit settings according to the rear screen connection videos.

Video ① https://youtube.com/shorts/amXbKgrQXeE

Video ② https://youtu.be/0bSB_584RLc

3. Try another HDMI cable.