Chosen Solution
MacBook Pro 15 laptop with Retina Display Mid 2014. Built in display quit working. I reset the NVRAM/PRAM and SMC, it worked for a couple days and then it went blank again. (back-light not coming on either) External monitor plugged into HDMI works. Comparing with my 2018, under About this Mac > System Report > Graphics/Displays, the Built-in Retina LCD is missing from the list. Only the HDMI screen is showing. As far as I know, there has never been any liquid spilled on it. Nor can I find any evidence internally of a liquid spill. Thanks
The first thing I would do is shine a flashlight through the apple logo on the display assembly to see if there is still image on the display and to see if the computer has a no back light issue. On many of retina macbook pro’s that I have worked on with a no display issues is the result of a bad display cable. These are fairly easy to replace. MacBook Pro 15" Retina Display Mid 2014 Display Assembly Replacement Both no display and no back light issues can be because of a bad display. Also check for corrosion on the logic board.
