CONNECTIVITY ISSUES RESULTING IN MONITOR NOT LIGHTING UP
For the moment, the LG UltraWide 5K monitor, model 34WK95U-W, is incompatible with the 15 inch MacBook Pro if both devices are connected to one another via Thunderbolt 3, and that will be until the next version of MacOS gets released, resulting in a Black Screen (No signal).
It has been reported and documented on the Internet that users have been experiencing issues with LG monitor, model number 34WK95U-W, whenever attempting to connect a 2018 15 inch MacBook Pro computer to the monitor via Thunderbolt 3 connection.
LG has been informed that this issue has been resolved with macOS10.14.2 beta2 update version. Apple released that new macOS version sometime in December 2018. Should you still be experiencing difficulties obtaining a picture on screen, please refer to below troubleshooting tips:
Further additional assistance can be located at the following link: Connecting external display to your MAC
This issue does not affect the 13 inch MacBook Pro computer.
For the time being, customers are asked to revert the connectivity between both devices by using USB-C to DisplayPort type. Customers will need to purchase that specific type of cable as it is not included with the monitor.
* Mac Devices, Personal Computers, Laptops
** Not included with monitor model 34WK95U-W