UE5 Failed to open map file. This is most likely because the map was saved with a newer version of the engine

"I am migrating a project from 4.27 to 5.0.0 early access 2 and I am getting the following message when I open the project:

“Failed to open map file. This is most likely because the map was saved with a newer version of the engine”.

I just followed the simple steps provided in the docs for the migration (Migration Guide | Unreal Engine Documentation), updating UE5 to the latest version and just opening a 4.27 project as a copy, like we all have done dozens of times with other projects.

Indeed, anything created in 4.27 is not visible in the content browser of UE5, although the files exist on disc.

Trying to debug it further I just created a blank project in 4.27, created a new map with a basic lighting setup and a simple material and did the same conversion process. In this case I didn´t get the error and the main default map just opened fine, but both the level I created as well as the shader are not being recognized and displayed in the content browser by the engine as in my original try.

While I am not an expert debugging UE logs, I don´t see any outstanding errors on it. I enclose it as well.
TEST.log (168.4 KB)

Has anybody else bumped into a similar situation and knows how to get this fixed? Does it look like a bug with the latest UE5 version?


Hey Martin!

Sorry to hear you’re having issues with the project you’re working on and work stoppage due to this. Unfortunately, 4.27 is not compatible with 5.0 Early Access. You can find more information on this here. Here is a screenshot from the ‘compatibility’ section.

Do you have a version of your project using 4.26 that you could migrate?

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Thanks a lot for the quick answer, it is indeed very informative.

I don´t have 4.26 version of it because it was already started in 4.27. There is not much done yet and I think it could probably be redone but I am wondering if it might be wiser to wait for the final release. Apparently Fortnite chapter 3 is already UE5, so I am wondering how long it will take to get the final version released.

there’s a 5.0 branch on github if you are willing to spend time on building it

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It is quite likely that I will take that path. Thanks for the pointers.