Failed to Load Assets when opening Level

First time this has happened and I’m not the only one.
“Failed to load assets” error message. - Development Discussion / Content Creation - Unreal Engine Forums

After zipping my entire project and transferring to another PC, I simply unzip and launch the project.
No error messages, a blank level opens. But when I try and launch any of my previously saved Maps nothing happens!
I get a popup saying 'Failed to Load Assets"

Additionally if i go to Project > Maps and Modes I am unable to change the Editor Startup Map to any of these previously saves maps.
Unreal 4.27 Windows.
Can anyone offer some troubleshooting steps? I’m googling but so far nothing.

OP Update
So apparently this is a version issue. I understand the need for not supporting backwards compatibility but this I don’t quite get. Running 4.27.0 on both machines!

CurrentEngineVersion: 4.27.0-16565192+++UE4+Release-4.27 (Licensee=0).
AssetEngineVersion: 4.27.0-16724560+++UE4+Release-4.27 (Licensee=0)