External monitors won't display when connected via docking station

[AKThompson]

I have an HP 255 G9 laptop. I want to connect two monitors so I have an HP Thunderbolt Dock G2. When I connect, the laptop will charge but the monitors will not display.  I've read that I may need an adapter but I want to see if anyone else can tell me what to do before I buy random stuff.

[Hawks_Eye]

Hi @AKThompson 

Welcome to the HP Support Community! We're here to help you get back up and running.

I understand the concern. Since the HP Thunderbolt Dock G2 is providing power but the monitors are not displaying, the key detail is that the HP 255 G9 Notebook PC is not a Thunderbolt-enabled platform. In many cases, charging can still work through the USB-C connection, but video output depends on the USB-C port supporting DisplayPort Alt Mode.

Before purchasing any adapter, please check the following:

1. Connect a single monitor directly to the notebook's HDMI port and confirm video output works.
2. Verify the exact HP 255 G9 configuration and whether the USB-C port supports video output (DisplayPort Alt Mode). Some HP 255 G9 models support data and charging only through USB-C.
3. Update the notebook BIOS and graphics drivers using HP Support Assistant or the HP support website.
4. Connect the dock and press Windows + P, then select Extend.
5. Open Settings > System > Display and select Detect to see if Windows recognizes the external monitors.
6. Check whether the monitors are detected in Device Manager > Monitors when connected through the dock.
7. If available, test the dock with another USB-C video-capable system to confirm the dock and monitors are functioning normally.

If your HP 255 G9 USB-C port does not support video output, the Thunderbolt Dock G2 will charge the notebook but will not provide display functionality. In that situation, a different connection method or compatible dock solution would be required.

Could you share the notebook's full product number (P/N) from the bottom label or HP System Information? That will help confirm whether your specific HP 255 G9 model supports video output over USB-C and whether any adapter would be needed.

Take care, and have an amazing day!

Regards, 

Hawks_Eye