macOS Mojave 10.14.x - impossible to download?

If there are any add-on anti-malware apps or add-on VPN apps or add-on cleaner apps on the 2015, remove those. Reboot the 2015 into Safe Mode, and try the Mojave link in the App Store app again.

Failing that, build a bootable installer for whatever version of macOS you can get, wipe the 2015, boot Recovery on the oldest available macOS (not the newest) for the 2015, and then try to upgrade that to Mojave.

a brody wrote:

To get Mojave, you must be running High Sierra or earlier, or a Mac that shipped with Mojave.

Macs that shipped with Mojave from can download it via command-option-shift-R at startup with a wired USB keyboard.

Some may download an older operating system than Mojave with that command, and that's fine. If you do download an older operating system, you can install it on a separate partition (minimum of 50 GB) or external hard drive, or flash drive formatted for HFS Extended GUID or APFS if available, and then follow these steps to upgrade.

You can't install Mojave on top of a working copy of Catalina or later. It must be the same or earlier operating system to take the installer.

Ah, yes, I missed that the user was trying a downgrade online.

That's not going to work.

Build a bootable installer, wipe, and start over.

There's nothing to restore, unless a backup from prior to Mojave is still around.

Files and settings that have been updated since Mojave doesn't work when restored on the older version.

Downloading Mojave from Monterey via the App Store does work, if the Mac supported Mojave. It just won't (directly) install. You do get an error when it tries to launch the installer. And it looks like that deletes the downloaded installer. Ugh.

You cannot get it anymore on a Mac that cannot run it. :(

On a Mac capable of running it try...

This Mac. These Mac models are compatible with macOS Mojave:

MacBook (Early 2015 or newer)

MacBook Air (Mid 2012 or newer)

MacBook Pro (Mid 2012 or newer)

Mac mini (Late 2012 or newer)

iMac (Late 2012 or newer)

iMac Pro (2017)

Mac Pro (Late 2013; Mid 2010 and Mid 2012 models with recommended Metal-capable graphics cards)

https://itunes.apple.com/us/app/macos-mojave/id1398502828?mt=12

If you are downgrading, follow the tips on this article:

How do I downgrade my Mac OS X operating … - Apple Community

Consecutive commands, same system, same session, less than a minute apart...

$ softwareupdate --list-full-installers
Finding available software
Software Update found the following full installers:
* Title: macOS Ventura, Version: 13.0, Size: 11866804KiB, Build: 22A380
* Title: macOS Monterey, Version: 12.6.1, Size: 12108491KiB, Build: 21G217
* Title: macOS Monterey, Version: 12.6, Size: 12104042KiB, Build: 21G115
* Title: macOS Monterey, Version: 12.5.1, Size: 12114929KiB, Build: 21G83
* Title: macOS Monterey, Version: 12.5, Size: 12112497KiB, Build: 21G72
* Title: macOS Big Sur, Version: 11.7.1, Size: 12119247KiB, Build: 20G918
* Title: macOS Big Sur, Version: 11.7, Size: 12118755KiB, Build: 20G817
* Title: macOS Big Sur, Version: 11.6.8, Size: 12118851KiB, Build: 20G730
* Title: macOS Big Sur, Version: 11.6.6, Size: 12121263KiB, Build: 20G624
* Title: macOS Big Sur, Version: 11.6.5, Size: 12121404KiB, Build: 20G527
* Title: macOS Big Sur, Version: 11.6.4, Size: 12147782KiB, Build: 20G417
* Title: macOS Big Sur, Version: 11.6.3, Size: 12143674KiB, Build: 20G415
* Title: macOS Big Sur, Version: 11.6.2, Size: 12141944KiB, Build: 20G314
* Title: macOS Big Sur, Version: 11.6.1, Size: 12137180KiB, Build: 20G224
* Title: macOS Big Sur, Version: 11.5.2, Size: 12149332KiB, Build: 20G95
* Title: macOS Catalina, Version: 10.15.7, Size: 8055650KiB, Build: 19H15
* Title: macOS Catalina, Version: 10.15.7, Size: 8055522KiB, Build: 19H2
* Title: macOS Catalina, Version: 10.15.6, Size: 8055450KiB, Build: 19G2021
* Title: macOS High Sierra, Version: 10.13.6, Size: 5099306KiB, Build: 17G66
$ softwareupdate --list-full-installers
Finding available software
Software Update found the following full installers:
* Title: macOS Ventura, Version: 13.0, Size: 11866804KiB, Build: 22A380
* Title: macOS Monterey, Version: 12.6.1, Size: 12108491KiB, Build: 21G217
* Title: macOS Monterey, Version: 12.6, Size: 12104042KiB, Build: 21G115
* Title: macOS Monterey, Version: 12.5.1, Size: 12114929KiB, Build: 21G83
* Title: macOS Monterey, Version: 12.5, Size: 12112497KiB, Build: 21G72
* Title: macOS Big Sur, Version: 11.7.1, Size: 12119247KiB, Build: 20G918
* Title: macOS Big Sur, Version: 11.7, Size: 12118755KiB, Build: 20G817
* Title: macOS Big Sur, Version: 11.6.8, Size: 12118851KiB, Build: 20G730
* Title: macOS Big Sur, Version: 11.6.6, Size: 12121263KiB, Build: 20G624
* Title: macOS Big Sur, Version: 11.6.5, Size: 12121404KiB, Build: 20G527
* Title: macOS Big Sur, Version: 11.6.4, Size: 12147782KiB, Build: 20G417
* Title: macOS Big Sur, Version: 11.6.3, Size: 12143674KiB, Build: 20G415
* Title: macOS Big Sur, Version: 11.6.2, Size: 12141944KiB, Build: 20G314
* Title: macOS Big Sur, Version: 11.6.1, Size: 12137180KiB, Build: 20G224
* Title: macOS Big Sur, Version: 11.5.2, Size: 12149332KiB, Build: 20G95
* Title: macOS Catalina, Version: 10.15.7, Size: 8055650KiB, Build: 19H15
* Title: macOS Catalina, Version: 10.15.7, Size: 8055522KiB, Build: 19H2
* Title: macOS Catalina, Version: 10.15.6, Size: 8055450KiB, Build: 19G2021
* Title: macOS Mojave, Version: 10.14.6, Size: 5896894KiB, Build: 18G103
* Title: macOS High Sierra, Version: 10.13.6, Size: 5099306KiB, Build: 17G66
$

Notice any difference there?

Checking the install log, InstallAssistantAuto.pkg is reporting an error.

$ softwareupdate --download --fetch-full-installer --full-installer-version  10.14.6
Scanning for 10.14.6 installer
Install failed with error: Installation failed 
Error Domain=PKDownloadError Code=8 "(null)" UserInfo={NSUnderlyingError=0x600001ac05a0 {Error Domain=PKDownloadError Code=14 "(null)"}} 
$

Based on download times, there's still a cached copy around somewhere, and I can't find it. Still rummaging.

TL;DR: This is far harder than it should be.

You can often get the old installers working—there’s usually a stale certificate embedded—by looking up the release date for the version, setting the system date manual and setting the date just after the release became available, then starting the installer, and once the installer is to the first prompt, reset the time correctly, and continue the install.

To get Mojave, you must be running High Sierra or earlier, or a Mac that shipped with Mojave.

Macs that shipped with Mojave from can download it via command-option-shift-R at startup with a wired USB keyboard.

Some may download an older operating system than Mojave with that command, and that's fine. If you do download an older operating system, you can install it on a separate partition (minimum of 50 GB) or external hard drive, or flash drive formatted for HFS Extended GUID or APFS if available, and then follow these steps to upgrade.

You can't install Mojave on top of a working copy of Catalina or later. It must be the same or earlier operating system to take the installer.

You can’t run Mojave on M1 without also enabling full-on hardware emulation. You might install and get a virtualization and emulation tool such as UTM to work here, but Apple silicon won’t run x86-64 code including that of macOS Mojave without added emulation. And if it does run, it’ll be slow.

We understand, I was just telling you what Apple now requires, which I disagree with but it is what it is... to download it you need a Mac that can run it to download it.

BTW, it would only be an Update if you had an earlier 10.14.x on that Mac that can rin it, otherwise it'd be an Upgrade or Downgrade.

What happens when you try...

https://itunes.apple.com/us/app/macos-mojave/id1398502828?mt=12