Can't connect two monitors via elgato 3 dock

Question

I've got a MBP 2020 with 4 thunderbolt displays and Intel Iris Plus Graphics + an Elgato 3 Thunderbolt Dock. I can't connect two displays (both Dell U2415) via the dock. I've connected one display via mini display to usb-c cable. This one works. I tried to connect the second one using an hdmi cable with an hdmi to usb-c dongle. This one doesn't work. The system doesn't register that monitor at all, like it's not connected. However, if I connect the monitor directly to the second thunderbolt dock of the computer, it works dine.

On a side note - I see that the dock isn't fully functional. There are 2 usb-a ports on the dock, but it looks like I can connect only one device to either of them. Tested this using three different docking stations and multiple monitors (same cables/dongles in all situations though).

Any help/advice would be greatly appreciated :).

Answer 1

First of all do you have the Elgato Thunderbolt 3 or the Thunderbolt 3 Pro Dock?

I'm going to assume you are using the Thunderbolt 3 Pro Dock, as the Thunderbolt 3 Dock does not have the ports to physically plug in two USB-C cables when connected to the Laptop.

The dock has 2x USB 3.1 type C connectors and two Thunderbolt 3 ports of one is the upstream port and the other one is connected to the Laptop. It also has a Displayport connector.

The problem you are having is that the two USB-C ports support data only. So my guess is that you connect the first display to the thunderbolt Port and the second one to a USB-C port which then is staying black.

The only way to connect two displays is using the Displayport and the thunderbolt 3 connector rather than the two adapters to USB-C. Ditch one adapter for a display port connection.

If any of my assumptions were wrong and this might change the perspective. Just let me know.