I had the same issue just now and I was looking for a solution in this forum, unfortunately I didn't find it. I've tried everything you have and I even put my logic board in the oven to perform a reflow and even that was no help. BUT As I kept digging I found something! What everyone experiencing this problem should try exactly this! I myself bought brand new RAM and replaced it so I believed that RAM wasn't the issue. But it ended up being a RAM issue. Not the RAM but the RAM SLOT itself! So please try this even if you think that RAM isn't the issue because I doubted it would work but now my Macbook is up and running!!!
Link to Youtube Video:
https://www.youtube.com/watch?v=xpagfXraSn4
Also try this as well:
https://www.youtube.com/watch?v=2vCpW2jCqmM