How to fix HDMI not working
Method 1:
Please follow the steps given below to uninstall the display driver.
a) Press Windows key + X key when you are at desktop.
b) Select Device Manager.
c) Find and double-click Display driver from the left panel to uninstall.
d) Right-click the device, and click Uninstall.
e) Windows will prompt you to confirm the device’s removal. Click OK to remove the driver.
f) After the uninstallation is complete, reboot your computer.
After you have successfully uninstalled the driver, please go to the computer manufacturer’s website, download the Windows 8.1 display driver for NVidia and check.
Method 2:
You may also check with LG support to see if you need to install any firmware updates for the TV.
You may also try running the Windows Updates and install all the available updates including the optional driver and firmware updates.
Windows Update: Frequently Asked Questions
You may also refer to the articles and check:
Get the best display on your monitor
Connect a second monitor or projector
Method 3:
Doing a clean boot to see if this is caused by a some third party services or not.The steps to do a clean boot are given in the link below.
www.support.microsoft.com/kb/331796
Method 4: Check the cables
See https://en.wikipedia.org/wiki/HDMI#Cables.
Are you sure your cable is of adequate quality, undamaged and with terminators properly connected to the cable?
Method 5: Uninstall the drivers
You must be logged on as an administrator to perform these steps.
b. On the “Device Manager” window, Select the device
c. Right Click on the device and click uninstall
d. Restart the computer once the driver is uninstalled.
Windows will inform you it doesn’t have the appropriate drivers — that’s error code 28.
![windows-unknown-device-properties[4]](https://cdn9.howtogeek.com/wp-content/uploads/2014/07/windows-unknown-device-properties4.png "windows-unknown-device-properties[4]")
Click the Details tab, click the Property box, and select Hardware Ids in the list. Windows displays a lot of other information about the device here, but the Hardware Ids will help you identify the device.
You’ll usually see a list of long strings of characters here. Just looking at them won’t tell you much, but they’re actually unique hardware IDs that correspond to the hardware.
Perform a web search for the hardware ID using your favorite search engine. You should find the name of the piece of hardware associated with the unknown device, and that will give you the information you need to hunt down the driver.
Here, we can see that the device is a Nexus 4 or Nexus 7 (2013) with USB Debugging enabled, so we’d need to install the ADB drivers. Windows will then recognize the ADB interface and the device will be a properly installed, “known device.”
![perform-web-search-for-hardware-ids[4]](https://cdn9.howtogeek.com/wp-content/uploads/2014/07/perform-web-search-for-hardware-ids4.png "perform-web-search-for-hardware-ids[4]")
Install the Driver
You can now hunt down the driver for the hardware device and install it normally. You shouldn’t have to mess with the Device Manager here — just install the driver using the standard installer and it should work.
If you have to manually install a driver for the device — perhaps the driver is already installed on your system — you can use the Update Driver button in the device’s Properties window. If the device driver is already installed on your system, click the “Browse my computer for driver software” link and choose an installed driver.
Automatically Identify Devices and Install Drivers.
To check whether this feature is enabled or disabled, open the Control Panel and click View devices and printers under Hardware and Sound. Right-click the device that represents your computer itself and select Device installation settings.
Ensure “Yes, do this automatically (recommended)” or at least “Always install the best driver software from Windows Update” is selected. These are the default settings, and allow Windows to download drivers and automatically configure new hardware.
After enabling this setting, click the Update Driver button in a device’s properties window in Device Manager. You’ll be able to search for drivers from Windows Update — this should happen automatically after you connect the device to the PC, but you may want to try it again if you’ve just re-enabled the feature.
Windows Update doesn’t have every driver for every device ever created. You’ll sometimes have to hunt the driver down on your own.
Unknown devices are often a problem after reinstalling Windows on a PC. If Windows can’t find all the drivers for your PC’s hardware, you’ll need to hunt down the drivers and install them yourself. They shouldn’t be a problem later on unless you upgrade your PC’s components or connect more exotic peripherals to it.
Method 7: RUN the Hardware Troubleshooter
If your computer is having problems with a recently installed device or other hardware, try using the Hardware and Devices troubleshooter to fix the problem. It checks for common issues and makes sure that any new device or hardware attached to your computer was installed correctly.
Note
To make sure you have the most up-to-date troubleshooters from the Windows Online Troubleshooting Service, your computer should be connected to the Internet. For more information, see Troubleshooting in Windows.
Open the Hardware and Devices troubleshooter by clicking the Start button 
, and then clicking Control Panel. In the search box, type troubleshooter, and then click Troubleshooting. Under Hardware and Sound, click Configure a device. 
If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
For Windows 8 and later Windows just type Hardware and Devices troubleshooter.