I can’t install MacOS I get a message saying that is not able.

I have a late 2008, early 2009, MacBook 5,1 that was running El Capitan (OS 10.11), but the HD was quirky. I was changing its use and decided to refresh it by erasing the disk and reinstalling El Capitan. What a challenge that was for the last week. The starting point was an old copy of Snow Leopard on a DVD, and my Apple id showed the purchase of Mavericls and El Capitan so that I was able to download the latter.

It was impossible to execute according to the instructions found on the machine or Apple Support, i.e., using the Recovery Disk partition, a Time Machine back-up and so on. Every time I was almost there, after El Cap installed, a message came up saying that the OS could not be installed to the disk. I believe that was because of the certificates problem cited elsewhere.

Also, the Terminal command listed by Apple is incorrect and I had to adapt it by adding the --nointeraction shown below or else all would fail at the last moment of password verification.

Here follows my solution, which has finally worked.

A complete backup on Time Machine is useful.

Get the El Capitan app into your Applications folder as cdescribed in the notes below.

A bootable USB is created on a volume named INSTALLER using the command below, as described in the notes.

Once booted up to the USB stick, a date change is required using Terminal prior to the installation, as described. This way, the install can occur using older certificates.

The creation of the bootable USB, the use of the "date" command in Terminal, and other items, are described in the notes below.

https://www.macissues.com/2015/10/01/how-to-overcome-os-x-10-11-el-capitan-not-installing/

AND

https://support.apple.com/en-us/HT201372

AND

https://discussions.apple.com/thread/251009047

For reference, and cut and paste use in Terminal, the creation of USB by instal command is:

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/INSTALLER --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app —nointeraction

Best of luck.

I am guessing that you are trying to install via Recovery. The version of El Capitan on the Recovery servers has not been updated since the certificates ran out, thus you can't install it. One quick workaround is to change the date and time set on your mac

using Terminal. Read this,

https://bensmann.no/changing-system-date-from-terminal-os-x-recovery/

I would suggest setting the date and time to Jan 4th 19:00hrs 2018 as below

date -u 0104190018

If this then allows you to download El Capitan you can change it back to the current date and time

when the installation is complete.

If you go here, you can download the updated version of El Capitan that has valid certificates,

How to upgrade to OS X El Capitan – Apple Support

At Section 4 download InstallMacOSX.dmg. When that has downloaded open it and you will get InstallMacOSX.pkg.

Double-click on that and an installation window will open, this will convert InstallMacOSX.pkg to the

Install OS X El Capitan.app which will be in your Applications folder.

Use the Install OS X El Capitan.app to create a new bootable USB installer, How to create a bootable installer for macOS – Apple Support

Please note you can only do this on macs that can run El Capitan or earlier, a mac that came preinstalled with macOS Sierra or newer can download the .dmg but will not convert the .pkg to the install app, as rather stupidly it thinks you are wanting to install El Capitan on the newer mac and not simply helping out one of its older stablemates.

What does Disk Utility say about the disk usage on your drive.

I asked you a question a week ago, are you going to answer it.

How much free space does your mac.