I’m encountering major issues with a UE5.4 C++ project that worked perfectly as recently as the night before the problems began. Without making any changes to the project or environment, Unreal Engine now fails to build the project, regenerate project files, or even launch properly. Below is a full breakdown of the symptoms, errors, attempted solutions, and system state to help expedite troubleshooting.
- Unreal Engine Version: 5.4.4 (installed via Epic Games Launcher)
- Project Type: C++ based, standard UE5 classes and plugin structure
- Build IDE: Visual Studio 2022 (Community Edition)
- System OS: Windows 11
- Version Control: GitHub
Summary of Core Issues
Compilation/Module Issues
- HDTS project fails to build due to missing or outdated modules.
- Error Message:
"Missing HDTS Modules - The following modules are missing or built with a different engine version: HDTS" - Regenerating project files fails through .uproject context menu or command line.
- UnrealEditor.exe fails to launch with the following error:
"The application was unable to start correctly (0xc0150002). Click OK to close the application." - Visual Studio errors:
CS0246: The type or namespace name 'UnrealBuildTool' could not be foundC4067: unexpected tokens following preprocessor directiveMSB3073: exited with code -1 during rebuildC4996: FBoneMirrorInfo is deprecated
Missing/Outdated Engine Headers
- Numerous .cpp files reference
ConcurrentLinearAllocator.h, but this header no longer exists inUE_5.4\Engine\Source\Runtime\Core\Public\HAL. - The engine appears to have removed or renamed it, but plugins and project files still depend on it.
No Changes Were Made Before Failure
- The project compiled, ran, and animated fine just the night before.
- No engine updates were applied by me.
- No plugin or dependency changes were made between the working and broken state.
Actions Taken to Fix It
Uninstalls / Reinstalls
- Fully uninstalled Unreal Engine 5.4.4 via Epic Games Launcher
- Fully uninstalled and reinstalled Visual Studio 2022 Community Edition, selecting:
- Workloads:
- Desktop Development with C++
- Game Development with C++
- Individual Components:
- MSVC v143 – Latest C++ toolset
- Windows 10 SDK (10.0.19041+)
- CMake tools for Windows
- .NET SDK (optional)
- Workloads:
Folder Cleanup
- Deleted Unreal-related folders in:
C:/Users/username/AppData/Local
Specifically removed:UnrealBuildToolUnrealEngineUnrealTrace- Kept only
UnrealEngineLauncher
- Cleared temporary build and intermediate files
- Ran Build > Clean Solution followed by Build > Rebuild Solution in Visual Studio
Project-Level Fix Attempts
- Right-clicked
.uprojectand attempted to rebuild - Attempted
UnrealEditor.exe -projectfilesbut Unreal fails to open - Verified existence of
ScriptCodeGeneratorBase.csand other plugin files - Verified missing
ConcurrentLinearAllocator.his still referenced but does not exist
- What happened to
ConcurrentLinearAllocator.hand why is it still being referenced by the engine/plugin files? - Why is
UnrealBuildToolno longer being detected, even after reinstalling both Visual Studio and UE5? - Is there an official patch, hotfix, or workaround for breaking plugin dependencies (especially for ScriptGeneratorUbtPlugin)?
- Should I roll back to a previous version of UE5.4 (if that’s even possible)?
- What is the best way to safely clean and regenerate UBT and plugin references?
Final Notes
- I have access to the full GitHub repo of the project.
- I’d be happy to share logs, reproduction steps, or even the full project folder if needed.