According to your description, I suggest you refer to the following information:
When your notebook is connected to an external monitor, the screen of the external monitor is normal and the screen of the notebook is blank. This situation is probably caused by laptop screen failure or poor cable contact. In order not to delay your use, it is suggested that you can contact the local HP Gold Service Center to help you detect and deal with it.
You can check the nearest HP Gold Service Center through the following website:
/zh/support-drivers/e support/as CPPS . html
I hope the above reply can help you.
If the above information can't solve your problem, you can log on to www.hp.com.cn/chat,, the online chat room of HP Network, and ask an online engineer to help you solve the problem further. More product information is available in www.hp.com.cn/800..