External widescreen display resolution of 2560x1080 is unavailable

[Big-Legow]

Hello, I hope someone out there can help me with this issue.

Issue: If I open my HP Elitebook laptop to use the built in display along with the 2 x external displays, the resolution of the LG widescreen switches to a lower resolution of 1920 x 1080, and there are no higher resolutions beyond 1920 x 10180 that allow me to select the required 2560 x 1080. The widescreen resolution of 2560x1080 is available and defaults to that when I close the laptop and only use the external monitors, or if i disconnect the other external non-widescreen monitor. 

Some more details that may help:

 - I have connected my HP EliteBook 755 G5 to 2 x external monitors via the HP Thunderbolt Dock 120W G2.

 - One of the external monitors is an LG widescreen that requires a resolution of 2560 x 1080.

 - I have connected the LG widescreen to the HP dock using an HDMI to DisplayPort cable (HDMI connected to the monitor).

 - I have connected the other external non-widescreen monitor using the Display Port on both monitor and Dock.

 - If I close the laptop and only use the external displays the resolution for the LG widescreen is supported and all works fine.

 - I have spent several hours on this now, switching out different cables, so I hope you can help me resolve this.

[banhien]

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@Big-Legow wrote:

...  - I have connected the LG widescreen to the HP dock using an HDMI to DisplayPort cable (HDMI connected to the monitor)...

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@Big-Legow 

There are few versions of HDMI cables. Have you tries DP to HDMI version 2.0 cable yet ?

Regards.

[Big-Legow]

@Banhein

Thanks for responding. Do you think the cable could be the problem, even though I can get the correct 2560x1080 resolution using the cable I have on the widescreen monitor if i do one of the following:

 1. Close the laptop over so I am only using the two external monitors (one of them being the widescreen)

 2. Keep the laptop open and disconnect the non-widescreen external monitor (so just using the laptop screen and the widescreen external display.

The issue of not being able to select the 2560x1080 resolution for the widescreen display only happens when my laptop is open and I am using the laptop screen, along with 2 x external monitors (one of which is the widescreen) .

Thanks, I appreciate your feedback, just want to check before I look to purchase another cable.