In case you missed it in the release notes for 4.1, there are some steps you may need to take to upgrade your project to load it in the 4.1 Editor.
Upgrading Blueprint-only projects
- You can load your existing project in the new editor normally.
- Note: Some Blueprint APIs may have changed between versions, which could cause warnings in your content. Read the API Changes section for more information.
Upgrading C++ code projects
- You’ll need to recompile the C++ project for the new version of Unreal Engine
- Locate the .uproject file in your game’s folder, and right click on it. (on Mac, you can also Command + Click)
- Select Switch Unreal Engine Version → 4.1 (on Mac, this is in a Services menu)
- Right click to generate new C++ project files, then recompile your game normally.
- Note: Some C++ APIs may have changed between versions, which can cause compile errors. Read the API Changes section for more information.
Full release notes can be found here, https://www.unrealengine.com/blog/41-release-notes
Sorry for the inconvenience, we’re going to work on a cleaner solution for future releases where this is more automated.
Cheers,
Nick