PowerExpand 8-in-1 display problems

I recently bought a PowerExpand 8-in-1 for a brand new HP Pavilion 14t-dv000 laptop, which has a one USB-C port with this spec: 1 SuperSpeed USB Type-C® 10Gbps signaling rate (USB Power Delivery, DisplayPort™ 1.4, HDMI 2.0, HP Sleep and Charge)

My plan was to use this to connect 2x Acer CB272U displays over HDMI, with QHD resolution (not sure if it would support 30hz or 60hz in that configuration). But I have not had any luck getting it to work. All the other ports, including ethernet, work fine, and Windows does recognize both monitors. But I am not getting any signal on the monitors, regardless of what resolution I select. If I plug them directly into the laptop, they work just fine. I tried changing the resolution on the monitors down to only 1920x1080 but I still get no signal. I tried only connecting one monitor, but that also doesn’t work.

The laptop has a brand new i5-1135G7 processor with integrated Intel Xe graphics, which, based on the spec sheet supports up to 4 displays at 4k@60 each. Obviously the USB-C can’t handle quite that, but I thought I should be able to comfortably drive 2x QHD displays? The laptop’s internal display is only a FHD.

Any thoughts? Am I dealing with a defective device?