Upgrading from Pre-High Sierra to Install Post-High Sierra:

A Manual Post-High Sierra macOS Install:

Do you have an operating system installed prior to High Sierra (macOS 10.13), and have unsuccessfully tried upgrading it to Mojave (MacOS 14) or thereafter?

First upgrade to High Sierra (macOS 10.13) and then proceed with the upgrade to Mojave (macOS 10.14) and other release from here-on-out.

-------

There are Five Steps to Follow:

1. First: create a Time Machine Backup (TMB) of your current Mac.
2. Erase: your disk
3. Install: High Sierra (macOS 10.13)
4. Upgrade: to Mojave (MacOS 14) or Thereafter
5. Migrate: Items over using Migration Assistant

Five Steps In Depth:

1. Back up your Mac:

Create a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with the transfer.

2. Erase your Disk

1. Boot: into Recovery Mode [Hold Down: command + R keys] upon boot
2. Select: Disk Utility
3. Erase: the hard drive

3. Install High Sierra:

Create and use a High Sierra USB Bootable Installer. Use a USB Flash Drive of 16GB to create it.

4. Upgrade to Mojave or Later:

Go Here: How to Create a Bootable Installer for macOS - Apple Support

5. Migrate and Reinstall Data and Apps:

Next migrate it over from the Time Machine Backup you created in Step 1.

Note: Some of your apps may not work with macOS Mojave (macOS 1t) and thereafter if they are not 64-bit. If something does not run in the new install, request from the developers new keys for the software. Inform them that your Mac has crashed, and that they give you the installation files you need (Ask for 64-bit installers).