Installing High Sierra on MacBook Pro from 2012
After formatting everything I had on my hard drive and reinstalling OS X Mountain Lion on the computer (the one that came originally with it) the App Store won't open up though logged in with my Apple ID, neither most web pages from Safari, like the official page of Apple. Normally, the only thing it allows me is search on Google.
I've tried to download the .dmg on my new Mac and, then, transferring it to the old one through USB, but when I open the installer the system tells me that it requieres the .0 version of the upgrade, and not the last one as is offered by Apple.
Also I've tried to create a bootable installer from the new Mac but, as it's not an Intel based one, the system doesn't let me install it.
I suppose that the principal problem is not being able to access to the App Store and the vast majority of web pages, but I don't know if it is due to an expiry of certificate or not (changing the date to 2012 hasn't work anyways)
MacBook Pro 15″