The LG Ultra Fine 4K display device called 22MD4KA is a monitor product that can be connected to a Mac device for use.
You can connect it to a Mac host that supports USB-C or Thunderbolt 3 for use.
The following is the list of devices supported and depending on the Mac host, different resolutions are supported.
4096 x 2304@60Hz supported
iMac(2017)
MacBook Pro(2016) and subsequent models
MacBook(2016) and subsequent models
4096 x 2304@48Hz supported
MacBook(2015) and subsequent models
Note that it is not compatible with Mac host using Thunderbolt 2.
Try this
Check the OS version.
You are recommended to use a Mac OS version subsequent to Sierra 10.12.3.
Check the cable used for a connection.
Use the USB-C cable provided in the basic package to connect to a Mac host.
This guide was created for all models, so the images or content may be different from your product.