PN50 - USB-C/Thunderbolt to 2x HDMI adapter not working

[yesyes]

Hi, I recently purchased this PN50 with AMD Ryzen 5 4500U because it says it supports up to 4 monitors. It has 1 HDMI port and the configurable port is a DisplayPort.
The remaining 2 monitors are to be connected via USB-C/Thunderbolt 3. For that purpose I purchased a StarTech Thunderbolt 3 to Dual HDMI Adapter (Mfr part code: TB32HD24K60).

However, I can't get this working. I keep getting a Windows message "Thunderbolt device functionality might be limited" when I plug in the adapter. See attached screenshot.

StarTech have a troubleshooting website that tells me to download the latest Thunderbolt FW at www.asus.com/support/. However, I can't find any Thunderbolt software on the ASUS support site (after selecting the PN50 product).

I found "ThunderBolt_Intel_Win10_64_VER16252250.zip" for one of the other products (a laptop I think) and installed that but I still have the same issue. When I run this software the list "Attached Devices Chains" is empty.

Does anyone know any solution for this issue, please? I specifically bought this PN50 to be able to run at least 3 monitors, ideally 4.
None of my monitors have direct Thunderbolt connections (only HDMI, DVI and VGA).

[xeromist]

Those aren't Thunderbolt ports, just USB-C. So you would need USB-C DP adapters. I'm not sure without further research whether there is a USB-C HDMI adapter that would work with the native DP output of those ports. A lot of USB HDMI adapters create a whole new virtual display device which might have inferior resolutions & refresh rates. For best results you might need a USB-C DP adapter and then a DP to HDMI adapter.