Thanks for reply.
I need to return to El Capitan to be compatible with other computers & software in my home. It really should be an easy task to return to the OSX but it has been a nightmare.
1_Installed Mountain Lion from Apple internet recovery.
2_Downloaded El Capitan 10.11.6 from Apple How to get old versions of macOS - Apple Support
but this version will NOT upgrade my Mountain Lion 10.8.5 to El Capitan 10.11.6. It goes through all the screens and appears to upgrade but when it reboots it is still on Mountain Lion 10.8.5. Nor does it install a Clean install without Mountain Lion. Tried it both ways.
3_When installing from an external boot drive, the process gets stuck and give warning something like this: Will not install "contact manufacturer and retry & restart".
4_When I try to reinstall from Apple internet restore I get: Will not install "contact manufacturer and retry & restart".
Then computer is stuck in install mode and is totally unusable.
5_Repeated the whole process of erasing disk, reinstalling all over again and the same problem occurs.
Absolutely no success! How do I get back to El Capitan?
Thanks for help!
