USB-C output to HDMI confusion

[suicidal_monkey]

I bought a basic usb-c to hdmi dongle.

On my laptop one of the two usb-c ports works as desired and I can output to two monitors (using the hdmi port on the laptop for the other display) so I know it works. Using the dongle in the other usb-c port results in Windows detecting display 3 in settings but there's no output to it.

On my wife's work laptop, when we plug the dongle in we get output to the monitor plugged in to the dongle but the laptop's own hdmi port then stops outputting...display settings only shows one external display...and I can't work out what setting to look for to make it continue to output to its own hdmi when the dongle is plugged in :sideways:

On my wife's personal laptop we don't get anything from the usb-c port, and looking at the symbols on it, it seems like the usb-c port is only usb2.0 and it's the "old-style" usb ports on it that are usb3.0 and I assume I need 3.0 for the hdmi to work(?) ...is that possible: USB-C can be only 2.0?

Three laptops, three results :g::help2:

Laptops:
- Gigabyte aero 15: works in one usb-c, not the other
- Lenovo thinkpad t490s: dongle works but the laptop hdmi stops working
- HP 15-cs0013na : dongle doesn't work, usb-c port maybe only v2.0?!

[smilodon]

Not sure if it helps (probably doesn't) but the usb-c to hdmi system uses HDMI v1.4b not the newer HDMI V2.0. Maybe the issue is that a specific HDMI port is configured to accept an HDMI 2.0 source but is getting only an HDMI 1.4b signal from the usb-c source. This might cause things to go a bit fubar? HDR video output for example needs HDMI 2 so won't work across a usb-c adapter

[suicidal_monkey]

Thanks Smilo but I don't think that's it - both monitors work from the dongle using the aero and the lenovo (though the lenovo's own built-in hdmi port then stops outputting video) so it seems to be that the HP is the only one not managing to output to hdmi through the dongle.

if it helps anyone the HP 15-cs0013na info page says that the usb-c port is "1 USB 3.1 Type-Câ,,¢ Gen 1 (Data Transfer up to 5 Gb/s, Power Delivery, DisplayPortâ,,¢ 1.2, HP Sleep and Charge)" ... so to my mind this suggests it should work :g: