Chosen Solution
Installed new logic board + SSD to my MPB 2015. Now I can’t install anything higher than Sierra. This always fails with a message about how “firmware verification failed”.
Any hints?
There’s a few different issues you could be facing! The first is if you are trying to install High Sierra or Mojave Apple messed up the certificates pre-maturing expiring them! Here’s more If you’ve got an old macOS install image, it will probably stop working today Here’s the fixed installers: How to upgrade to macOS High SierraHow to upgrade to macOS Mojave If you where trying to install Catalina, there have been reports of problems with the updater. So its important to first upgrade in order through the releases and then go to Catalina. If that fails visit an Apple Store so they can fix it.
