Reinstall Mac OS X issue - ‘This item is temporarily unavailable’

The certificates for several of Apples OS's expired in October 2019, Apple have been very poor at getting these updated on their Recovery Servers with valid certificates. This may be the problem you are experiencing. 

Try this workaround, we are going to set the time and date on your mac to a date previous to the expiry date of the certificates.

It would be best if you could connect your mac to your router via cable, as you have a MacBook use a Thunderbolt or USB to Ethernet cable.

Boot to your Recovery HD, click on Utilities in the menubar select Terminal.

Make sure WiFi is switched off, it can reset the date back to today.

Enter a new date, for example or just copy and paste

sudo date -u 011421002016

press Return

enter your password

press Return

If Terminal returns an error saying sudo : command not found, then try again without sudo.

Now try downloading the OS.

If this works then when the OS is installed and booted up you can Open System Preferences> Date & Time

and reset the time back to today.

So basically your friend just stuck the Install macOS High Sierra.app on the USB.

Well that's no use to anyone.

You wiped your mac, so it has no OS on it, so nothing can happen till you get

an OS installed on it.

Even if you did manage to get Lion installed via the Recovery Servers you would

not be able to install High Sierra as it needs at least Mountain Lion to install.

If your friend has a mac that is running El Capitan or at some point could run El Capitan

then get him to download El Capitan from here,

(please note you cannot do this on a mac that came preinstalled with 

Sierra, High Sierra, Mojave or Catalina.)

How to upgrade to OS X El Capitan – Apple Support

Give him these instructions.

Go to Section 4 and click on Download OS X El Capitan.

This downloads InstallMacOSX.dmg to your Downloads folder.

When downloaded open to InstallMacOSX.pkg, double-click on

that and an installation window will open, this does not install El Capitan

but converts the .pkg to the Install OS X El Capitan.app which you will find in 

your Applications folder, it should be 6.2GBs in size.

Now create a bootable USB installer disk, using the Install OS X El Capitan.app

in the Applications folder, and the createinstallmedia command in the Terminal app. 

Read the instructions here,

How to create a bootable installer for macOS – Apple Support

Well you could get him to make you a bootable USB with High Sierra as well if you want, my only concern about that is

your mac was trying to install Mac OS X Lion. And any mac running Mac OS X Lion cannot upgrade directly to High Sierra.

I said before for your mac to upgrade to High Sierra it would need to be running Mac OS X Mountain Lion.

so for this reason I think your mac may not have the necessary firmware to install High Sierra. That is why I suggested

El Capitan. I wouldn't go on anything Apple support says.

So get your friend to make two bootable USB installers, one with El Capitan and one with High Sierra.

Try installing High Sierra first and if it does not work try installing El Capitan.

Hello,

Is your Macintosh connected to the internet?

Yeah I don't know what Apple are playing at these days, a lot of people are reporting problems trying to install legacy OS's from their servers.

Have you booted to the High Sierra USB installer, Restart your mac, whilst pressing and holding the option/ alt key,

after a couple of minutes you should see the Startup Manager, a graphical representation of the bootable drives attached to your mac, select the USB and press Return. The mac will restart and boot to the USB. Once it has booted up you will see a Utilities panel, click on Install OS and press Continue.

See if it works, it may not.

Is this USB with High Sierra actually a bootable USB created by using the createinstallmedia command in Terminal

How to create a bootable installer for macOS – Apple Support or using an app like DiskMaker or similar.

Or is it just a USB stick with the High Sierra installer on it., there is a big difference.