Chosen Solution
After the Mac not starting up i made a bootable installer when prompted to install el capitan error message this copy install os x el capitan can’t be verified. It may be damaged or was manipulated when it was downloaded. I made a new bootable installer on 4 different usb drives 16gb but get same error code. Attempts to restore or download os x on the faulty mac everything seems to work fine untill the end of the process. But then get the message could not install OS X el capitan. i checked the disks and diagnosed everything i could with the tools i’ve got. No problems found. Apple support first willing to send me the command for the terminal to fix this backed with explanation certain things and commands are secret and cannot be send.
You’re not crazy! Apple messed us up! Here’s more on the issue If you’ve got an old macOS install image, it will probably stop working today To fix this you’ll need to get the fixed installer or you need to fake-out the installer! We have updated installers for Sierra through to Mojave from Apple. But if you want to use El Capitan we will need the fake-out method! So here we need to do alter the systems clock setting back dating it back to the year the OS installer certificate is valid for. So here El Capitan was released in Sept 2015 so setting the year setting to let say 2017 will meet the certificates window to work! So now using your USB OS installer you have now. Open the control panel altering things as I’ve outlined here. Remember set the year to 2017
Now reboot your system and let the installer rip! Done! Don’t forget to reset the year back to today afterwards.
