This happens if you tried the GitHub build but didn't run Setup.bat before moving offline. The batch file downloads third-party libraries (like PhysX, Oculus SDK). You must run Setup.bat on an internet machine before transferring.
No internet required on the second machine; works without the launcher. You lose access to the Unreal Marketplace and easy project management tools. Epic Games Developers Offline Installer of Unreal Engine - Epic Games Developers download unreal engine 4.27 offline installer
If you require a completely independent installation without the Epic Launcher, you can build it from source. Link your Epic Games account to GitHub . Clone Repository: Download the 4.27 branch source code. Setup: Run Setup.bat to download dependencies. This happens if you tried the GitHub build
Unfortunately, Epic Games does not provide an official, single-file offline installer for Unreal Engine 4.27 (or any recent version). The standard installation method requires the Epic Games Launcher to download and verify files. No internet required on the second machine; works