U2723QE, MacBook Pro M3 Pro, USB-C port #8 issue

Hello,

I recently purchased a Dell U2723QE monitor and connected it to my MacBook Pro M3 Pro via the 90W USB-C port (5) at the back. Everything works perfectly with this setup. However, when I connect an SSD to the second USB-C port (8) at the back of the monitor, it does not mount on my Mac. Interestingly, when I connect the same SSD to the third USB-C port (15) located on the side of the monitor, it works fine. Can you help me understand why this is happening?

Thank you for your assistance.

Mike