Updrading a 2013 MacBook pro retina from Yosemite to a newer OS X version fails
I both downloaded and tried to install El Capitan and Sierra and followed the installation instructions via How to download macOS - Apple Support
In both cases I did not get any error messages while downloading and installing. But after a very and probably too fast fast installation, a successful installation message appeared. But the macbook, even after a reboot was still running Yosemite.
The MacBook is a MacBook Pro 2013 with a retina screen and has 4GB RAM. Why isn't it upgrading and what can or should I do to upgrade it? I hope someone can give me a helpful tip. Thanks in advance.