Chosen Solution
I was editing a video in Premiere and my screen randomly turned grey. When I rebooted, I got the chime and the click touchpad, but also a grey screen. I tried reseting my PRAM, SMC, booting in safe mode, and nothing worked. Then I picked up my laptop and started banging it with my fists. Hard. And now it’s working. This is the second time it’s given me the grey screen recently, the first time no keyboard solutions worked, and the first literally hitting it worked. What’s going on that would cause my fist to fix the problem? Loose wires or something?
It could be that wires in the display flex cable are dying. When you bang on your laptop, it might push some cables into temporary contact. When it greys out again, try opening/closing the display a few times to see if anything changes. If it does, the cable is wearing out at the hinge. You can try to re-seat the display connector. Follow this guide to remove the bottom panel out, disconnect the battery (for safety), then skip to Step 10 to disconnect the display connector. MacBook Pro 15" Retina Display Mid 2015 Display Assembly Replacement
Sounds like it could be a loose LCD cable, or a faulty inverter. I would recommend replacing the display assembly and LCD cable for a permanent solution.
Thanks everyone for the advise, will try these things. My issue is, I don’t know if it’s a fuse,inverter,cable issue and so I don’t want to spend any money replacing something that may be fine
