I got a very odd problem after updating to 10.12.5 and I'll try explaining it to the best I can along all troubleshooting I did...
I have a Macbook Pro retina 13" (early 2015) that I've always used with two Samsung external monitors (both are the same model). One of them is connected directly through the HDMI port located on the right side of the Macbook Pro, the other one connected through a thunderbolt-to-HDMI cable. It has always worked until last week when I updated to 10.12.5.
After the update, I quickly noticed that my Macbook Pro wouldn’t detect any external display via thunderbolt-to-HDMI. Thus, I started a long process of troubleshooting, and here’s all I’ve tried:
Assuming it could have been a defective cable, I’ve tried 3 different ones, still no luck
I’ve tried both thunderbolt entry, still no luck
I’ve tried thunderbolt-to-VGA, it WORKS, yes, I know this is insane.
I’ve tried to connect thunderbolt-to-HDMI (still with all 3 cables) on older Samsung monitors (again two older monitors were the same model, it was my old setup)… it worked
Then, I assumed it was the Samsung monitors that were broken (the two of them at the same time…? Odd, isn’t it?). Thus, I tried to connect them on my mac mini, the same way I always did on my Macbook pro… And it works…
Then I tried to reproduce the problem on my mom’s Macbook Pro retina 13” (exact same model I have the problem with and same update)... It works
Then I assumed the problem must be coming from my Macbook Pro. Thus, I booted on Windows 8 (bootcamp), it works.
Starting to lose my mind… I booted from an external hard drive I have (running an early sierra version), it didn’t work either (I had used this external hard drive in the past and it was WORKING)
I've done a factory reset, still not working
EDIT (forgot to mention):
SMC, no luck
NVRAM, no luck
So in a nutshell, the problem seems to appear only via thunderbolt-to-HDMI, only on this specific Macbook Pro, and specifically on macOS.
I’m no expert and I don’t know what else I can do. Of course I've tried contacting Apple many times but they keep blaming me for updating my mac and/or Samsung for making the environment not compatible, which I believe is a total nonsense.
Has anyone encounter any similar problem? Does anyone know what it could be?
I’m desperate so I’d like to thank y’all in advance for your help.